Oracle Notes

SQL

SQL stands for "Structured Query Language". It is used by Relational DataBase technologies

such as Oracle, Microsoft Access, and Sybase, among others. SQL lets you access and

manipulate databases. SQL is an ANSI (American National Standards Institute) standard. SQL

can execute queries against a database. SQL can retrieve data from a database. SQL can insert

records in a database. SQL can update records in a database. SQL can delete records from a

database. SQL can create new databases. SQL can create new tables in a database. SQL can

create stored procedures in a database. SQL can create views in a database. SQL can set

permissions on tables, procedures, and views. Although SQL is an ANSI (American National

Standards Institute) standard, there are many different versions of the SQL language. However,

to be compliant with the ANSI standard, they all support at least the major commands (such as

SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner.

Note: Most of the SQL database programs also have their own proprietary extensions in addition

to the SQL standard! sequel – (Structured English Query Language)”.

RDBMS

RDBMS stands for Relational Database Management System. RDBMS is the basis for SQL, and

for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft

Access. The data in RDBMS is stored in database objects called tables. A table is a collections of

related data entries and it consists of columns and rows.

SQL Commands

SQL commands are instructions used to communicate with the database to perform specific

task that work with data. SQL commands can be used not only for searching the database

but also to perform various other functions like, for example, you can create tables, add

data to tables, or modify data, drop the table, set permissions for users. SQL commands are

grouped into four major categories depending on their functionality:

Data Definition Language (DDL) - These SQL commands are used for creating,

modifying, and dropping the structure of database objects. The commands are

CREATE, ALTER, DROP, RENAME, and TRUNCATE.

Data Manipulation Language (DML) - These SQL commands are used for

storing, retrieving, modifying, and deleting data. These commands are SELECT,

INSERT, UPDATE, and DELETE.

Transaction Control Language (TCL) - These SQL commands are used for

managing changes affecting the data. These commands are COMMIT, ROLLBACK,

and SAVEPOINT.

Data Control Language (DCL) - These SQL commands are used for providing

security to database objects. These commands are GRANT and REVOKE.

SQL SELECT Statement

The most commonly used SQL command is SELECT statement. The SQL SELECT

statement is used to query or retrieve data from a table in the database. A query may

retrieve information from specified columns or from all of the columns in the table. To

create a simple SQL SELECT Statement, you must specify the column(s) name and the

table name. The whole query is called SQL SELECT Statement.

Syntax of SQL SELECT Statement:

SELECT column_list FROM table_name

[WHERE Clause]

[GROUP BY Clause]

[HAVING Clause]

[ORDER BY Clause];

DataBase Table “student_details”:

ID FIRST_NAME LAST_NAME AGE SUBJECT GAMES

1 Pravesh Shrivastava 24 CSE Football

2 Nitin Singh 25 CSE Cricket

3 Akhilesh Kumar 25 CSE Cricket

4 Abhishek Tripathi 26 CSE Cricket

5 Priyanka Ghosh 25 CSE Basketball

To select the First Name of all the students the query would be like:

select first_name from student_details;

Output:

FIRST_NAME

Pravesh

Priyanka

Nitin

Akhilesh

Abhishek

You can also retrieve data from more than one column. For example, to select First Name

and Last Name of all the students.

select first_name, last_name from student_details;

Output:

FIRST_NAME LAST_NAME

Pravesh Shrivastava

Priyanka Ghosh

Nitin singh

Akhilesh Kumar

If we want to display the First and Last Name of a student combined together, the SQL Select

Statement would be like: select first_name ||’’|| last_name from student_details;

Output:

FIRST_NAME||' ' | |LAST_NAME

Pravesh Shrivastava

Nitin Singh

Akhilesh Kumar

Abhishek Tripathi

Priyanka Ghosh

You can also provide Alias as below.

select first_name ||’’|| last_name as Name from student_details;

Output:

NAME

Pravesh Shrivastava

Nitin Singh

Akhilesh Kumar

Abhishek Tripathi

Priyanka Ghosh

SQL DISTINCT STATEMENT

In a table, some of the columns may contain duplicate values. This is not a problem, however,

sometimes you will want to list only the different (distinct) values in a table. The DISTINCT

keyword can be used to return only distinct (different) values.

SQL SELECT DISTINCT Syntax

SELECT DISTINCT column_name(s) FROM table_name

To select all distinct subject names from student_details table, the query would be:

select distinct subject from student_details;

Output:

SUBJECT

CSE

SQL WHERE Clause

The WHERE Clause is used when you want to retrieve specific information from a table

excluding other irrelevant data. So SQL offers a feature called WHERE clause, which we

can use to restrict the data that is retrieved. The condition you provide in the WHERE

clause filters the rows retrieved from the table and gives you only those rows which you

expected to see. WHERE clause can be used along with SELECT, DELETE, UPDATE

statements.

Syntax of SQL WHERE Clause:

SELECT column_list FROM table_name WHERE condition;

To find the first name of a student with id 1, the query would be like:

select first_name from student_details where id=1;

Output:

FIRST_NAME

Pravesh

SQL Operators

There are two type of Operators, namely Comparison Operators and Logical Operators.

These operators are used mainly in the WHERE clause, HAVING clause to filter the data to

be selected.

Comparison Operators:

Comparison operators are used to compare the column data with specific values in a

condition.

Comparison Operators are also used along with the SELECT statement to filter data based

on specific conditions.

The below table describes each comparison operator.

Comparison

Operators Description

= equal to

<>, != is not equal to

< less than

> greater than

>= greater than or equal

to

<= less than or equal to

Logical Operators:

There are three Logical Operators namely, AND, OR, and NOT. These operators

compare two conditions at a time to determine whether a row can be selected for the output.

When retrieving data using a SELECT statement, you can use logical operators in the

WHERE clause, which allows you to combine more than one condition.

Logical

Operators Description

OR For the row to be selected at least one of

the conditions must be true.

AND For a row to be selected all the specified

conditions must be true.

NOT For a row to be selected the specified

condition must be false.

"OR" Logical Operator:

If you want to select rows that satisfy at least one of the given conditions, you can use the

logical operator, OR.

For example: if you want to find the names of students who are studying either CSE or

ECE, the query would be like,

SELECT first_name, last_name, subject

FROM student_details

WHERE subject = 'CSE' OR subject = 'ECE';

Output:

FIRST_NAME LAST_NAME SUBJECT

Pravesh Shrivastava CSE

Nitin Singh CSE

Akhilesh Kumar CSE

Abhishek Tripathi CSE

Priyanka Ghosh CSE

"AND" Logical Operator:

If you want to select rows that must satisfy all the given conditions, you can use the logical

operator, AND.

For Example: To find the names of the students between the age 24 to 26 years, the query

would be like:

SELECT first_name, last_name, age


WHERE age >= 24 AND age <= 26;

Output:

FIRST_NAME LAST_NAME AGE

Pravesh Shrivastava 24

Nitin Singh 25

Akhilesh Kumar 25

Abhishek Tripathi 26

Priyanka Ghosh 25

"NOT" Logical Operator:

If you want to find rows that do not satisfy a condition, you can use the logical operator,

NOT. NOT results in the reverse of a condition. That is, if a condition is satisfied, then the

row is not returned.

For example: If you want to find out the names of the students who do not play football,

the query would be like:

SELECT first_name, last_name, games


WHERE NOT games = 'Football'

Output:

FIRST_NAME LAST_NAME GAMES

Nitin Singh Cricket

Akhilesh Kumar Cricket

Abhishek Tripathi Cricket

Priyanka Ghosh Basketball

Nested Logical Operators:

You can use multiple logical operators in an SQL statement. When you combine the logical

operators in a SELECT statement, the order in which the statement is processed is

1) NOT

2) AND

3) OR

For example: If you want to select the names of the students who age is between 24 and 26

years, or those who do not play football, the SELECT statement would be

SELECT first_name, last_name, age, games


WHERE age >= 24 AND age <= 26

OR NOT games = 'Football';

Output:

FIRST_NAME LAST_NAME AGE GAMES

Pravesh Shrivastava 24 Football

Nitin Singh 25 Cricket

Akhilesh Kumar 25 Cricket

Abhishek Tripathi 26 Cricket

Priyanka Ghosh 25 Basketball

SQL ORDER BY

The ORDER BY clause is used in a SELECT statement to sort results either in ascending or

descending order. Oracle sorts query results in ascending order by default.

Syntax for using SQL ORDER BY clause to sort data is:

SELECT column-list

FROM table_name [WHERE condition]

[ORDER BY [column1, column2, .. columnN] [DESC];

Database Table "student_details":

select id,first_name,last_name,age,subject,games from student_details order by id

Output:





4 Abhishek Tripathi 26 CSE Cricket


If you want to sort the student_details table by the name and age, the query would be like,

SELECT first_name, age FROM student_details ORDER BY first_name, age;

Output:

FIRST_NAME AGE

Abhishek 26

Akhilesh 25

Nitin 25

Pravesh 24

Priyanka 25

NOTE:The columns specified in ORDER BY clause should be one of the columns selected

in the SELECT column list.

You can represent the columns in the ORDER BY clause by specifying the position of a

column in the SELECT list, instead of writing the column name.

The above query can also be written as given below,

SELECT first_name, age FROM student_details ORDER BY 1, 2;

Output:

FIRST_NAME AGE

Abhishek 26

Akhilesh 25

Nitin 25

Pravesh 24

Priyanka 25

By default, the ORDER BY Clause sorts data in ascending order. If you want to sort the

data in descending order, you must explicitly specify it as shown below.

SELECT first_name, age FROM student_details ORDER BY first_name, age

desc;

Output:

FIRST_NAME AGE

Abhishek 26

Akhilesh 25

Nitin 25

Pravesh 24

Priyanka 25

The above query sorts only the column 'age' in descending order and the column 'first_name'

by ascending order.

If you want to select both first_name and age in descending order, the query would be as

given below.

SELECT first_name, age FROM student_details ORDER BY first_name

desc, age desc;

Output:

FIRST_NAME AGE

Priyanka 25

Pravesh 24

Nitin 25

Akhilesh 25

Abhishek 26

How to use expressions in the ORDER BY Clause?

For example: If you want to display student_details first_name, age, and a 20% increase in the

age for only those students for whom the percentage increase in age is greater than 30, the

SELECT statement can be written as shown below

SELECT first_name, age, age*1.2 AS new_age


WHERE age*1.2 > 30

ORDER BY new_age DESC;

Output:

FIRST_NAME AGE NEW_AGE

Abhishek 26 31.2

NOTE: Aliases defined in the SELECT Statement can be used in ORDER BY Clause.

SQL INSERT Statement

The INSERT Statement is used to add new rows of data to a table.

We can insert data to a table in two ways,

1) Inserting the data directly to a table.

Syntax for SQL INSERT is

INSERT INTO TABLE_NAME

[ (col1, col2, col3,...colN)]

VALUES (value1, value2, value3,...valueN);

While inserting a row, if you are adding value for all the columns of the table you need not

specify the column(s) name in the sql query. But you need to make sure the order of the values

is in the same order as the columns in the table. The sql insert query will be as follows

INSERT INTO TABLE_NAME

VALUES (value1, value2, value3,...valueN);

For Example: If you want to insert a row to the employee table, the query would be like,

insert into student_details (id,first_name,last_name,age,subject,games)

values(1,'Pravesh','Shrivastava',24,'CSE','Football')

Output:



NOTE: When adding a row, only the characters or date values should be enclosed with single

quotes.

If you are inserting data to all the columns, the column names can be omitted. The above insert

statement can also be written as,

insert into student_details values (3,’Nitin’,’Singh’,24,’CSE’,’Cricket’);

Output:





Inserting data to a table through a select statement:

Syntax for SQL INSERT is:

INSERT INTO table_name

[(column1, column2, ... columnN)]

SELECT column1, column2, ...columnN

FROM table_name [WHERE condition];

For Example: To insert a row into the student_details table from emp_net table, the sql insert

into query would be like,

emp_net table:

EMP_ID EMP_NAME

1 Ranjita

INSERT INTO student_details (id, first_name) SELECT emp_id, emp_name

FROM emp_net;

Output:





1 Ranjita - - - -

If you are inserting data to all the columns, the above insert statement can also be written as,

stu_net table:

STU_ID STU_F_NAME STU_L_NAME STU_AGE STU_SUB STU_GAMES


INSERT INTO student_details

SELECT * FROM stu_net;

Output:

NOTE:We have assumed the stu_net table has columns stu_id, stu_f_name, stu_l_name,

stu_age, stu_sub, stu_ games the above given order and the same datatype.

IMPORTANT NOTE:

1) When adding a new row, you should ensure the datatype of the value and the column

matches

2) You follow the integrity constraints, if any, defined for the table.





1 Ranjita - - - -


SQL UPDATE Statement

The UPDATE statement is used to update existing records in a table.

SQL UPDATE Syntax:

UPDATE table_name

SET column1=value2, column2=value2,...

WHERE some_column=some_value;

If we are updating the table student_details where first_name is Ranjita. The query would be

like:

update student_details set last_name='Kapoor', age=25,

subject='BSC',games='Badminton' where first_name='Ranjita';

Output:





1 Ranjita Kapoor 25 BSC Badminton


Note: Notice the WHERE clause in the UPDATE syntax. The WHERE clause specifies which

record or records that should be updated. If you omit the WHERE clause, all records will be

updated!

update student_details set last_name='Kapoor', age=25;

Output:


1 Pravesh Kapoor 25 CSE Football

2 Priyanka Kapoor 25 CSE Basketball

3 Nitin Kapoor 25 CSE Cricket

1 Ranjita Kapoor 25 BSC Badminton

4 Akhilesh Kapoor 25 CSE Cricket

To change the salaries of all the employees, the query would be,

update employee set salary=salary*2;

employee table:

ID NAME SALARY

1 Pravesh 19000

2 Nitin 19000

3 aaa 500

Output:

ID NAME SALARY

1 Pravesh 38000

2 Nitin 38000

3 aaa 1000

SQL DELETE Statement

The DELETE statement is used to delete records in a table. The DELETE statement is used to

delete rows in a table.

SQL DELETE Syntax:

DELETE FROM table_name

WHERE some_column=some_value;

If we want to delete the record where first name is Ranjita, the query would be like:

delete from student_details where first_name='Ranjita';

Output:

Note: Notice the

WHERE clause in the DELETE syntax. The WHERE clause specifies which record or records

that should be deleted. If you omit the WHERE clause, all records will be deleted!

Delete All Rows

It is possible to delete all rows in a table without deleting the table. This means that the table

structure, attributes, and indexes will be intact:

DELETE FROM table_name;

or

DELETE * FROM table_name;

Example:

delete from student_details;

Or

delete * from student_details;

Note: Be very careful when deleting records. You cannot undo this statement!


1 Pravesh Shrivastava 24 CSE Tennis


3 Nitin singh 25 CSE Cricket


You may wish to check for the number of rows that will be deleted. You can determine the

number of rows that will be deleted by running the following SQL statement before performing

the delete.

SELECT count(*)


WHERE first_name = 'Pravesh';

Output:

COUNT(*)

1

The ROWNUM Clause

The ROWNUM clause is used to specify the number of records to return. The ROWNUM clause

can be very useful on large tables with thousands of records. Returning a large number of records

can impact on performance.

Note: Not all database systems support the TOP clause.

Syntax:

SELECT column_name(s)

FROM table_name

WHERE ROWNUM <= number;

Example:

Now we want to select only the two first records in the table. We use the following SELECT

statement:

select * from student_details where rownum <=3;

Output:





SQL LIKE Operator

The LIKE operator is used to list all rows in a table whose column values match a specified

pattern. It is useful when you want to search rows to match a specific pattern, or when you do not

know the entire value. The LIKE condition allows you to use wildcards in the where clause of an

SQL statement. This allows you to perform pattern matching. The LIKE condition can be used in

any valid SQL statement - select, insert, update, or delete. The patterns that you can choose from

are:

% allows you to match any string of any length (including zero length).

_ allows you to match on a single character.

Examples using % wildcard:

We are going to try to find all of the person whose first name begins with 'Pr'.

select* from student_details

where first_name like 'Pr%';

Output:




You can also using the wildcard multiple times within the same string. For example,

In this example, we are looking for all persons whose first name contains the characters 'Pra'.

select * from student_details

where first_name like '%Pra%';

Output:



You could also use the LIKE condition to find persons whose first name does not start with 'P'.

For example,


where first_name not like 'P%';

By placing the not keyword in front of the LIKE condition, you are able to retrieve all suppliers

whose name does not start with 'P'.

Output:




Examples using _ wildcard:

Remember that the _ is looking for only one character. For example,

select * from student_details where first_name like 'Pr_yanka%';

Output:



Examples using Escape Characters:

Next, in Oracle, let's say you wanted to search for a % or a _ character in a LIKE

condition. You can do this using an Escape character. Please note that you can define an escape

character as a single character (length of 1) ONLY. For example,

select * from student_details where first_name like '%' escape '!';

This example returns all persons whose first name starts with any of the words and ends

in %. For example, it would return a value such as 'Pravesh%'.

Output:






select * from student_details where first_name like 'P%' escape '!';

This example returns all persons whose first name starts with P and ends in _. For

example, it would return a value such as 'Pravesh_'.

Output:




SQL Wildcards

SQL wildcards can substitute for one or more characters when searching for data in a database.

SQL wildcards must be used with the SQL LIKE operator. With SQL, the following wildcards

can be used:

Wildcard Description

% A substitute for zero or more characters

_ A substitute for exactly one character

[charlist] Any single character in charlist

SQL Wildcard Examples

Using the % Wildcard:

Now we want to select the students whose first names start with "Pr" from the

"student_details" table. We use the following SELECT statement:

select * from student_details where first_name like 'Pr%';

Output:

Next, we want to select the students whose subjects contain the pattern "CSE" from the

"student_details" table. We use the following SELECT statement:

select * from student_details where subject like '%CSE%';

Output:






Using the _ Wildcard:

Now we want to select the students with the first name that starts with any character,

followed by "ravesh" from the "student_details" table. We use the following SELECT statement:

select * from student_details where first_name LIKE '_ravesh%';




Output:



SQL IN Function

The IN function helps reduce the need to use multiple OR conditions. The syntax for the IN

function is:

SELECT columns

FROM tables

WHERE column1 in (value1, value2, .... value_n);

This SQL statement will return the records where column1 is value1, value2..., or value_n. The

IN function can be used in any valid SQL statement - select, insert, update, or delete. Example:

The following is an SQL statement that uses the IN function:

select * from student_details where first_name in ('Pravesh','Priyanka','Santosh');

Output:




This would return all rows where the first name is either Pravesh, Priyanka, or Santosh.

Because the * is used in the select, all fields from the student_details table would appear in the

result set.

It is equivalent to the following statement:

select * from student_details where first_name = 'Pravesh' OR first_name =

'Priyanka' OR first_name = 'Santosh';

Output:




As you can see, using the IN function makes the statement easier to read and more efficient.

Example:

You can also use the IN function with numeric values.

select * from student_details where id in (1,2,3,4,5,6);

Output:






This SQL statement would return all students where the id is either 1, 2, 3, 5, or 6.

It is equivalent to the following statement:

select * from student_details where id=1 or id=2 or id=3 or id=4 or id=5 or id=6;

Output:






Example:

The IN function can also be combined with the NOT operator.

select * from student_details where first_name not in ('Pravesh', 'Santosh', 'Nitin');

Output:




This would return all rows where the first_name is neither Pravesh, Santosh, nor Nitin.

Sometimes, it is more efficient to list the values that you do not want, as opposed to the values

that you do want.

SQL BETWEEN Operator

The BETWEEN operator is used in a WHERE clause to select a range of data between two

values. The values can be numbers, text, or dates.

SQL BETWEEN Syntax:


FROM table_name

WHERE column_name

BETWEEN value1 AND value2;

Now we want to select the students with a last name alphabetically between "Kumar" and

"Shrivastava" from the table above. We use the following SELECT statement:

select * from student_details where last_name between 'Kumar'and 'Shrivastava';

Output:

Note: The BETWEEN operator is treated differently in different databases. In Oracle, persons

with the Last Name of "Kumar" or "Shrivastava" will be listed, because the BETWEEN operator

selects fields that are between and including the test values.

To display the students outside the range in the previous example, use NOT BETWEEN:

select * from student_details where last_name not between 'Kumar' and

'Shrivastava';

Output:







SQL Alias

With SQL, an alias name can be given to a table or to a column. You can give a table or a

column another name by using an alias. This can be a good thing to do if you have very long or

complex table names or column names. An alias name could be anything, but usually it is short.

SQL Alias Syntax for Tables:


FROM table_name

AS alias_name;

SQL Alias Syntax for Columns:

SELECT column_name AS alias_name

FROM table_name;

Or

SELECT column_name ALIAS_NAME FROM table_name;

Table level alias:

select s.id,s.first_name from student_details s;

Output:

Column Level alias:

select id, first_name as name from student_details;

Output:

The above query is same like:

ID FIRST_NAME

1 Pravesh

2 Priyanka

3 Nitin

4 Akhilesh

ID NAME

1 Pravesh

2 Priyanka

3 Nitin

4 Akhilesh

select student_details.id, student_details.first_name from student_details;

Output:

ID FIRST_NAME

1 Pravesh

2 Priyanka

3 Nitin

4 Akhilesh

SQL Joins

The JOIN keyword is used in an SQL statement to query data from two or more tables, based on

a relationship between certain columns in these tables. Tables in a database are often related to

each other with keys. A primary key is a column (or a combination of columns) with a unique

value for each row. Each primary key value must be unique within the table. The purpose is to

bind data together, across tables, without repeating all of the data in every table.

Or

SQL Joins are used to relate information in different tables. A Join condition is a part of the sql

query that retrieves rows from two or more tables. A SQL Join condition is used in the SQL

WHERE Clause of select, update, delete statements. If a sql join condition is omitted or if it is

invalid the join operation will result in a Cartesian product. The Cartesian product returns a

number of rows equal to the product of all rows in all the tables being joined. For example, if the

first table has 20 rows and the second table has 10 rows, the result will be 20 * 10, or 200 rows.

This query takes a long time to execute.

Or

A join is used to combine rows from multiple tables. A join is performed whenever two or more

tables is listed in the FROM clause of an SQL statement.

Different SQL JOINs:

JOIN: Return rows when there is at least one match in both tables.

LEFT JOIN: Return all rows from the left table, even if there are no matches in the right

table.

RIGHT JOIN: Return all rows from the right table, even if there are no matches in the

left table.

FULL JOIN: Return rows when there is a match in one of the tables.

1) SQL Equi Joins:

An equi-join is further classified into two categories:

a) SQL Inner Join

b) SQL Outer Join

(a) SQL INNER JOIN

The INNER JOIN keyword return rows when there is at least one match in both tables. All

the rows returned by the sql query satisfy the sql join condition specified. It is the most

common type of join. Inner joins return all rows from multiple tables where the join

condition is met.

Table: suppliers:

Table: orders:

All the rows returned by the sql query satisfy the sql join condition specified.

For example: If you want to display the product information for each order the query will

be as given below. Since you are retrieving the data from two tables, you need to identify

the common column between these two tables, which is the supplier_id. The query for this

type of sql joins would be like,

select order_id, supplier_name from suppliers, orders where orders.supplier_id =

suppliers.supplier_id;

Output:

ORDER_ID SUPPLIER_NAME

50012 IBM

50013 Hewlett Packard

The rows for Microsoft and NVIDIA from the supplier table would be omitted, since the

supplier_id's 10002 and 10003 do not exist in both tables.

SUPPLIER_ID SUPPLIER_NAME

10000 IBM


10002 Microsoft

10003 NVIDIA

ORDER_ID SUPPLIER_ID ORDER_DATE

50012 10000 17-AUG-11

50013 10001 18-AUG-11

The columns must be referenced by the table name in the join condition, because

supplier_id is a column in both the tables and needs a way to be identified. This avoids

ambiguity in using the columns in the SQL SELECT statement.

The number of join conditions is (n-1), if there are more than two tables joined in a query

where 'n' is the number of tables involved. The rule must be true to avoid Cartesian product.

We can also use aliases to reference the column name, then the above query would be like,

select o.order_id, s.supplier_name from suppliers s, orders o where o.supplier_id =

s.supplier_id;

Output:

The rows for Microsoft and NVIDIA from the supplier table would be omitted, since the

supplier_id's 10002 and 10003 do not exist in both tables.

INNER JOIN (SQL SERVER)

select suppliers.supplier_name, orders.order_date, orders.order_id from orders inner

join suppliers on orders.supplier_Id=suppliers.supplier_Id;

Or

select suppliers.supplier_name, orders.order_date, orders.order_id from suppliers

inner join orders on suppliers.supplier_Id=orders.supplier_Id;

Or

select supplier_name, order_date, order_id from orders inner join suppliers

on orders.supplier_Id=suppliers.supplier_Id;

Or (With Alias)

select s.supplier_name, o.order_date, o.order_id from orders o inner join suppliers s

on o.supplier_Id=s.supplier_Id;

ORDER_ID SUPPLIER_NAME

50012 IBM


Output:

SUPPLIER_NAME ORDER_DATE ORDER_ID

IBM 17-AUG-11 50012

Hewlett Packard 18-AUG-11 50013

(b) SQL OUTER JOIN This sql join condition returns all rows from both tables which satisfy the join

condition along with rows which do not satisfy the join condition from one of the

tables. The sql outer join operator in Oracle is (+) and is used on one side of the join

condition only. This type of join returns all rows from one table and only those rows

from a secondary table where the joined fields are equal (join condition is met).

Note: The syntax differs for different RDBMS implementation. Few of them represent

the join conditions as "sql left outer join", "sql right outer join".

(a) Left Outer Join If you want to display all the suppliers data along with orders data, with null values

displayed for orders if a supplier has no order_id, the sql query for outer join would be

as shown below:

select s.supplier_id, s.supplier_name, o.order_id, o.order_date from orders o,

suppliers s where o.supplier_id (+) = s.supplier_id;

Output:

Or

The LEFT JOIN keyword returns all rows from the left table, even if there are no

matches in the right table.

SQL Server Syntax:

SELECT column_name(s)FROM table_name1 LEFT JOIN table_name2

ON table_name1.column_name=table_name2.column_name; SQL Server Query:

select suppliers.supplier_id, suppliers.supplier_name, orders.order_id from

suppliers left join orders on suppliers.supplier_Id=orders.supplier_Id order by

suppliers.supplier_name;

Output:

If we revert the query:

select suppliers.supplier_id, suppliers.supplier_name, orders.order_id from

orders left join suppliers on suppliers.supplier_id=orders.supplier_id order by

suppliers.supplier_name;

Output:

SUPPLIER_ID SUPPLIER_NAME ORDER_ID ORDER_DATE

10000 IBM 50012 17-AUG-11

10001 Hewlett Packard 50013 18-AUG-11

10002 Microsoft - -

10003 NVIDIA - -

SUPPLIER_ID SUPPLIER_NAME ORDER_ID

10001 Hewlett Packard 50013

10000 IBM 50012

10002 Microsoft -

10003 NVIDIA -



10000 IBM 50012

(b) RIGHT OUTER JOIN The RIGHT JOIN keyword Return all rows from the right table, even if there are no matches in the left

table.

NOTE: If the (+) operator is used in the left side of the join condition it is equivalent to left outer join.

If used on the right side of the join condition it is equivalent to right outer join.

select s.supplier_id, s.supplier_name, o.order_id, o.order_date from suppliers s, orders o

where o.supplier_id = s.supplier_id(+);

Output:


10000 IBM 50012 17-AUG-11


select s.supplier_id, s.supplier_name, o.order_id, o.order_date from suppliers s, orders o

where s.supplier_id = o.supplier_id (+);

Output:


10000 IBM 50012 17-AUG-11


10002 Microsoft - -

10003 NVIDIA - -

SQL Server Syntax:

SELECT column_name(s)FROM table_name1 RIGHT JOIN table_name2 ON

table_name1.column_name=table_name2.column_name;

SQL Server Example (1):

select suppliers.supplier_id, suppliers.supplier_name, orders.order_id, orders.order_date

from suppliers right join orders on suppliers.supplier_id = orders.supplier_id;

Output:


10000 IBM 50012 17-AUG-11




from orders right join suppliers on suppliers.supplier_id = orders.supplier_id;

Output:


10000 IBM 50012 17-AUG-11


10002 Microsoft - -

10003 NVIDIA - -



from suppliers right join orders on orders.supplier_id = suppliers.supplier_id;

Output:


10000 IBM 50012 17-AUG-11



from orders right join suppliers on orders.supplier_id = suppliers.supplier_id;

Output:


10000 IBM 50012 17-AUG-11


10002 Microsoft - -

10003 NVIDIA - -

SQL FULL Join The FULL JOIN keyword return rows when there is a match in one of the tables.

Syntax:


FROM table_name1

FULL JOIN table_name2

ON table_name1.column_name=table_name2.column_name;

Example:

Now we want to list all the suppliers and their orders, and all the orders with their persons.

select suppliers.supplier_id, suppliers.supplier_name, orders.order_id from suppliers full

join orders on suppliers.supplier_Id = orders.supplier_Id;

Output:


10000 IBM 50012


10002 Microsoft -

10003 NVIDIA -

The FULL JOIN keyword returns all the rows from the left table, and all the rows from the

right table. If there are rows in "suppliers" that do not have matches in "Orders", or if there are rows in

"Orders" that do not have matches in "suppliers", those rows will be listed as well.

SQL SELF JOIN

A Self Join is a type of sql join which is used to join a table to itself, particularly when the

table has a FOREIGN KEY that references its own PRIMARY KEY. It is necessary to

ensure that the join statement defines an alias for both copies of the table to avoid column

ambiguity.

Example:

select s.supplier_id, s.supplier_name, o.order_id from suppliers s, orders o where

s.supplier_id = o.supplier_id;

Output:


10000 IBM 50012


SQL UNION Operator

The UNION operator is used to combine the result-set of two or more SELECT statements.

Notice that each SELECT statement within the UNION must have the same number of columns.

The columns must also have similar data types. Also, the columns in each SELECT statement

must be in the same order. It removes duplicate rows between the various "select" statements. SQL UNION Syntax:

SELECT column_name(s) FROM table_name1

UNION

SELECT column_name(s) FROM table_name2;

Example:

select supplier_id from suppliers union select supplier_id from orders;

Output:

In this example, if a supplier_id appeared in both the suppliers and orders table, it would appear

once in your result set. The UNION removes duplicates.

Example: With ORDER BY Clause

The following is a UNION query that uses an ORDER BY clause:

select supplier_id

from suppliers

where supplier_id > 200

union

select order_id

from orders

where order_id > 1000

ORDER BY 1;

Since the column names are different between the two "select" statements, it is more

advantageous to reference the columns in the ORDER BY clause by their position in the result

set. In this example, we've sorted the results by supplier_id / order_id in ascending order, as

denoted by the "ORDER BY 1".

The supplier_id / order_id fields are in position #1 in the result set.

SUPPLIER_ID

10000

10001

10002

10003

SQL UNION ALL

The UNION ALL query allows you to combine the result sets of 2 or more "select" queries. It

returns all rows (even if the row exists in more than one of the "select" statements).

Each SQL statement within the UNION ALL query must have the same number of fields in the

result sets with similar data types.

UNION ALL Syntax:

SELECT column_name(s) FROM table_name1

UNION ALL

SELECT column_name(s) FROM table_name2; Example:

select supplier_id

from suppliers

union all

select supplier_id

from orders;

Output:

If a supplier_id appeared in both the suppliers and orders table, it would appear multiple times in

your result set. The UNION ALL does notremove duplicates.

Example:

select supplier_id from suppliers where supplier_id > 200

union all

select order_id from orders where order_id > 1000

order by 1;

Output:

SUPPLIER_ID

10000

10001

10002

10003

10000

10001

SUPPLIER_ID

10000

10001

10002

10003

50012

50013

SQL CREATE TABLE Statement

The CREATE TABLE Statement is used to create tables to store data. Integrity Constraints like

primary key, unique key, foreign key can be defined for the columns while creating the table.

The integrity constraints can be defined at column level or table level. The implementation and

the syntax of the CREATE Statements differs for different RDBMS.

CREATE TABLE Statement Syntax:

CREATE TABLE table_name

(column_name1 datatype,

column_name2 datatype,

... column_nameN datatype

);

Example: If you want to create the employee table, the statement would be like,

create table employee

( id number(5),

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10)

);

CREATE a table from another table

You can also create a table from an existing table by copying the existing table's columns.

It is important to note that when creating a table in this way, the new table will be populated with

the records from the existing table (based on the SELECT Statement).

Syntax: Copying all columns from another table

CREATE TABLE new_table

AS (SELECT * FROM old_table);

Example:

create table new_table

as (select * from company);

Syntax: Copying selected columns from another table


AS (SELECT column_1, column2, ... column_n FROM old_table);

Example:

create table supply_new

as (select id, city, state

from supply

where id = 1);

Syntax: Copying selected columns from multiple tables


AS (SELECT column_1, column2, ... column_n

FROM old_table_1, old_table_2, ... old_table_n);

Example:

create table supply_new_new

as (select supply.id, supply.address, orders.order_id from supply, orders

where orders.order_id = supply.id

and id = 1);

SQL Constraints

Constraints are used to limit the type of data that can go into a table. Constraints can be specified

when a table is created (with the CREATE TABLE statement) or after the table is created (with

the ALTER TABLE statement). We will focus on the following constraints:

NOT NULL

UNIQUE

PRIMARY KEY

FOREIGN KEY

CHECK

DEFAULT

Constraints can be defined in two ways:

1) The constraints can be specified immediately after the column definition. This is called

column-level definition.

2) The constraints can be specified after all the columns are defined. This is called table-level

definition.

SQL NOT NULL Constraint

The NOT NULL constraint enforces a column to NOT accept NULL values. The NOT NULL

constraint enforces a field to always contain a value. This means that you cannot insert a new

record, or update a record without adding a value to this field.

Example with Constraint:


( id number(5),

name char(20) constraint nm_nn not null,

dept char(10),

age number(2),

salary number(10),

location char(10)

);

Or

Example without Constraint:


( id number(5),

name char(20) not null,

dept char(10),

age number(2),

salary number(10),

location char(10)

);

SQL UNIQUE Constraint

The UNIQUE constraint uniquely identifies each record in a database table. The UNIQUE and

PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of

columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it.

Note that you can have many UNIQUE constraints per table, but only one PRIMARY KEY

constraint per table.

Example:


( id number(5),

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10) UNIQUE

);

Or


( id number(5)not null unique,

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10) unique

);

Or


( id number(5),

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10) constraint loc_un unique

);

Or


(id number(5),

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10),

constraint loc_un unique(location)

);

Or


(id number(5),

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10),

constraint loc_un unique(location, name)

);

SQL UNIQUE Constraint on ALTER TABLE

To create a UNIQUE constraint on the "id" column when the table is already created, use the

following SQL:

Add Unique constraint without constraint:

alter table employee

add unique(id);

Add Unique constraint with constraint:


add constraint uc_e_id unique(id,name);

To allow naming of a UNIQUE constraint, and for defining a UNIQUE constraint on multiple

columns, use the following SQL syntax:


add constraint uc_e_id unique(id,name);

To DROP a UNIQUE Constraint


drop constraint uc_e_id;

SQL PRIMARY KEY Constraint

This constraint defines a column or combination of columns which uniquely identifies each row

in the table.

Primary Key on Create Table:

Primary Key at column level without Constraint:


(id number(5) primary key,

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10)

);

Primary Key at column level with Constraint:


(id number(5) constraint emp_id_pk primary key,

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10)

);

Primary Key at table level:


(id number(5),

name char(20),

dept char(10),

age number(2),

salary number(10),

location char(10),

constraint emp_id_pk primary key(id)

);

SQL PRIMARY KEY Constraint on ALTER TABLE

Add Primary Key without Constraint:


add primary key (id);

Add Primary Key with Constraint:


add constraint p_k_e_id primary key(id);

To DROP a PRIMARY KEY Constraint


drop constraint p_k_e_id;

SQL Foreign key or Referential Integrity This constraint identifies any column referencing the PRIMARY KEY in another table. It

establishes a relationship between two columns in the same table or between different

tables. For a column to be defined as a Foreign Key, it should be a defined as a Primary Key

in the table which it is referring. One or more columns can be defined as Foreign key.

Foreign Key at column level with constraint:


(id number(5) constraint e_id_pk primary key,

name char(20),

dept char(20),

age number(10)

);

create table company

(c_id number(2) primary key,

c_name char(20),

id number(2) constraint c_e_id references employee(id)

);

Foreign Key at column level without constraint:



name char(20),

dept char(20),

age number(10)

);


(c_id number(2) primary key,

c_name char(20),

id number(2)references employee(id)

); Table Colum n Data Type Length Precision Scale Prim ary Key Nullable Default Comm ent

EMPLOYEE32 ID Number - 5 0 1 - - -

NAME Char 20 - - - - -

DEPT Char 20 - - - - -

AGE Number - 10 0 - - -

Foreign Key at table level:


(id number(5),

name char(20),

dept char(20),

age number(10),

constraint e_id primary key(id)

);


(c_id number(2),

c_name char(20),

id number(2),

constraint c_c_id primary key(c_id),

constraint c_e_id foreign key(id) references employee(id)

);

SQL FOREIGN KEY Constraint on ALTER TABLE

Add Foreign Key without constraint:

alter table company

add foreign key (order_id)

references orders(order_id);

Add Foreign Key with constraint:

alter table company

add constraint fk_o_id

foreign key (order_id)

references orders(order_id);

To DROP a FOREIGN KEY Constraint

alter table company

drop constraint fk_o_id;

SQL CHECK Constraint

The CHECK constraint is used to limit the value range that can be placed in a column.

If you define a CHECK constraint on a single column it allows only certain values for this

column. If you define a CHECK constraint on a table it can limit the values in certain columns

based on values in other columns in the row.

Column Level SQL CHECK Constraint on CREATE TABLE without constraint:



name char(20),

dept char(10),

age number(2),

gender char(1) check (gender in ('M','F')),

salary number(10),

location char(10)

);

Column Level SQL CHECK Constraint on CREATE TABLE with constraint:



name char(20),

dept char(10),

age number(2),

gender char(1) constraint c_e_id check (gender in ('M','F')),

salary number(10),

location char(10)

);

Table Level SQL CHECK Constraint on CREATE TABLE with constraint:



name char(20),

dept char(10),

age number(2),

gender char(1),salary number(10),

location char(10),

constraint c_e_id check (gender in ('M','F'))

);

SQL CHECK Constraint on ALTER TABLE

Without Constraint:


add check (id>0);

Or

Check on multiple columns:


add check (id>0 and gender='M');

With Constraint:


add constraint chk_emp check (id>0 and gender='M');

To DROP a CHECK Constraint


drop constraint chk_emp;

SQL DEFAULT Constraint

The DEFAULT constraint is used to insert a default value into a column.

The default value will be added to all new records, if no other value is specified.

SQL DEFAULT Constraint on CREATE TABLE:

create table person_details

(p_id number not null,

name char(20),

address varchar(200),

city char(255) default 'Gwalior'

);

SQL CREATE INDEX Statement

An index can be created in a table to find data more quickly and efficiently. The users cannot see

the indexes, they are just used to speed up searches/queries. Index in sql is created on existing

tables to retrieve the rows quickly. When there are thousands of records in a table, retrieving

information will take a long time. Therefore indexes are created on columns which are accessed

frequently, so that the information can be retrieved quickly. Indexes can be created on a single

column or a group of columns. When an index is created, it first sorts the data and then it assigns

a ROWID for each row.

Note: Updating a table with indexes takes more time than updating a table without (because the

indexes also need an update). So you should only create indexes on columns (and tables) that

will be frequently searched against.

SQL CREATE INDEX Syntax:

Creates an index on a table. Duplicate values are allowed:

Syntax:

CREATE INDEX index_name

ON table_name (column_name);

Example:

create index person_index on person_details(p_id);

SQL CREATE INDEX on multiple columnsSyntax:

CREATE INDEX index_name

ON table_name (column_name1,column_name2...);

SQL CREATE UNIQUE INDEX Syntax:

Creates a unique index on a table. Duplicate values are not allowed:

Syntax:

CREATE UNIQUE INDEX index_name

ON table_name (column_name);

Example:

create unique index index_person

on person_details (city,address);

In Oracle there are two types of SQL index namely, implicit and explicit.

Implicit Indexes:

They are created when a column is explicity defined with PRIMARY KEY, UNIQUE KEY

Constraint.

Explicit Indexes:

They are created using the "create index.. " syntax.

NOTE:

1) Even though sql indexes are created to access the rows in the table quickly, they slow

down DML operations like INSERT, UPDATE, DELETE on the table, because the indexes

and tables both are updated along when a DML operation is performed. So use indexes only

on columns which are used to search the table frequently.

2) Is is not required to create indexes on table which have less data.

3) In oracle database you can define up to sixteen (16) columns in an INDEX.

SQL DROP

Indexes, tables, and databases can easily be deleted/removed with the DROP statement.

The SQL DROP command is used to remove an object from the database. If you drop a table, all

the rows in the table are deleted and the table structure is removed from the database. Once a

table is dropped we cannot get it back, so be careful while using DROP command. When a table

is dropped all the references to the table will not be valid.

The DROP INDEX Statement

Syntax:

DROP INDEX index_name;

Example:

drop index index_person;

The DROP TABLE Statement

Syntax:

DROP TABLE table_name;

Example:

Drop table employee;

SQL TRUNCATE Statement

The SQL TRUNCATE command is used to delete all the rows from the table and free the space

containing the table.

Syntax:

TRUNCATE TABLE table_name;

Example:

truncate table employee;

Difference between DELETE and TRUNCATE Statements: DELETE Statement: This command deletes only the rows from the table based on the

condition given in the where clause or deletes all the rows from the table if no condition is

specified. But it does not free the space containing the table.

TRUNCATE statement: This command is used to delete all the rows from the table and

free the space containing the table.

SQL ALTER TABLE Statement

The SQL ALTER TABLE command is used to modify the definition (structure) of a table

by modifying the definition of its columns. The ALTER command is used to perform the

following functions.

1) Add, drop, modify table columns

2) Add and drop constraints

3) Enable and Disable constraints

Syntax to add a column:

ALTER TABLE table_name ADD column_name datatype;

Example:

alter table student_details add salary number(5);

Output:

ID FIRST_N AME LAST_NAME AGE SUBJECT GAMES SALARY

1 Pravesh Shrivastava 24 CSE Tennis -

2 Priyanka Ghosh 25 CSE Basketball -

3 Nitin singh 25 CSE Cricket -

4 Akhilesh Kumar 25 CSE Cricket -

Syntax to drop a column:

ALTER TABLE table_name DROP column column_name;

Example:

alter table student_details drop column salary;

Output:






Syntax to modify a column:

ALTER TABLE table_name MODIFY column_name datatype;

Example:

alter table student_details modify salary char(20);

SQL RENAME Command

The SQL RENAME command is used to change the name of the table or a database object.

If you change the object's name any reference to the old name will be affected. You have to

manually change the old name to the new name in every reference.

Syntax:

RENAME old_table_name To new_table_name;

Example:

rename student_details to student_info;

SQL AUTO INCREMENT Field

Auto-increment allows a unique number to be generated when a new record is inserted into a

table. Very often we would like the value of the primary key field to be created automatically

every time a new record is inserted. We would like to create an auto-increment field in a table.

You will have to create an auto-increment field with the sequence object (this object generates a

number sequence).

Use the following CREATE SEQUENCE syntax:

CREATE SEQUENCE seq_name

MINVALUE min_value

START WITH start_value

INCREMENT BY increment_value

CACHE end_value;

Example:

create sequence seq_emp

minvalue 1

start with 1

increment by 1

cache 10;

The code above creates a sequence object called seq_emp, that starts with 1 and will

increment by 1. It will also cache up to 10 values for performance. The cache option specifies

how many sequence values will be stored in memory for faster access.

To insert a new record into the "emp_details" table, we will have to use the nextval

function (this function retrieves the next value from seq_emp sequence):

create table emp_details

(id number(5),

name char(20),

age number(2)

);

insert into emp_details(id,name,age) values(seq_emp.nextval,'Pravesh',25);

SQL CREATE VIEW Statement

In SQL, a view is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database. You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the data were coming from one single table.

A view is, in essence, a virtual table. It does not physically exist. Rather, it is created by a query

joining one or more tables.

A VIEW is a virtual table, through which a selective portion of the data from one or more tables

can be seen. Views do not contain data of their own. They are used to restrict access to the

database or to hide data complexity. A view is stored as a SELECT statement in the database.

DML operations on a view like INSERT, UPDATE, DELETE affects the data in the original

table upon which the view is based.

SQL CREATE VIEW Syntax:

CREATE VIEW view_name AS

SELECT columns

FROM table

WHERE predicates;

Example:

create view sup_order2 as

select supplier_id, supplier_name

from suppliers;

Updating a VIEW

You can update a VIEW without dropping it by using the following syntax.

CREATE OR REPLACE VIEW view_name AS

SELECT columns

FROM table

WHERE predicates;

Example:

create or replace view sup_order2 as

select supplier_id,supplier_name

from suppliers;

Dropping a VIEW

The syntax for dropping a VIEW is:

DROP VIEW view_name;

SQL: Data Types

The following is a list of general SQL datatypes that may not be supported by all relational

databases.

Data Type Syntax Explanation (if applicable) Range

Integer integer

Smallint smallint

Numeric numeric(p,s) Where p is a precision value; s is a

scale value. For example,

numeric(6,2) is a number that has 4

digits before the decimal and 2

digits after the decimal.

Precision can

range from 1 to

38.

Decimal decimal(p,s) Where p is a precision value; s is a

scale value.

Where p is the

precision and s

is the scale.

For example,

decimal(3,1) is

a number that

has 2 digits

before the

decimal and 1

digit after the

decimal.

Real real Single-precision floating point

number

double precision double precision Double-precision floating point

number

Float float(p) Where p is a precision value.

Character char(x) Where x is the number of characters

to store. This data type is space

padded to fill the number of

characters specified.

Maximum size

of 2000 bytes.

character varying varchar2(x) Where x is the number of characters

to store. This data type does NOT

space pad.

Maximum size

of 4000 bytes

Bit bit(x) Where x is the number of bits to

store.

bit varying bit varying(x) Where x is the number of bits to

store. The length can vary up to x.

Date date Stores year, month, and day values. A date between

Jan 1, 4712 BC

and Dec 31,

9999 AD.

Time time Stores the hour, minute, and second

values.

Timestamp timestamp Stores year, month, day, hour,

minute, and second values.

fractional

seconds

precision must

be a number

time with time zone time with time zone Exactly the same as time, but also

stores an offset from UTC of the

time specified.

timestamp with time

zone

timestamp with time

zone

Exactly the same as timestamp, but

also stores an offset from UTC of

the time specified.

fractional

seconds

precision must

be a number

between 0 and

9. (default is 6)

year-month interval Contains a year value, a month

value, or both.

day-time interval Contains a day value, an hour

value, a minute value, and/or a

second value.

nchar(size) nchar(x)

Where size is the number of

characters to store. Fixed-length

NLS string Space padded.

Maximum size

of 2000 bytes.

SQL Functions

SQL has many built-in functions for performing calculations on data.

SQL Aggregate Functions:

SQL aggregate functions return a single value, calculated from values in a column.

Useful aggregate functions:

AVG() - Returns the average value

COUNT() - Returns the number of rows

MAX() - Returns the largest value

MIN() - Returns the smallest value

SUM() - Returns the sum

SQL Scalar functions:

SQL scalar functions return a single value, based on the input value.

Useful scalar functions:

UCASE() - Converts a field to upper case

LCASE() - Converts a field to lower case

MID() - Extract characters from a text field

LEN() - Returns the length of a text field

ROUND() - Rounds a numeric field to the number of decimals specified

NOW() - Returns the current system date and time

FORMAT() - Formats how a field is to be displayed

SQL AVG() Function

SQL AVG(): This function is used to get the average value of a numeric column.

SQL AVG() Syntax:

SELECT AVG(column_name) FROM table_name;

Example:

select avg(age) from student_details;

Output:

AVG( AGE)

24.75

SQL COUNT() Function

This function returns the number of rows in the table that satisfies the condition specified in the

WHERE condition. If the WHERE condition is not specified, then the query returns the total

number of rows in the table.

SQL COUNT(column_name) Syntax: The COUNT(column_name) function returns the number of values (NULL values will not be

counted) of the specified column.

SELECT COUNT(column_name) FROM table_name;

Example:

select count(subject) from student_details;

Output:

SQL COUNT(*) Syntax:

The COUNT(*) function returns the number of records in a table:

SELECT COUNT(*) FROM table_name;

Example:

select count(*) from student_details;

Output:

COUNT(SUBJECT)

4

COUNT(*)

4

SQL MAX() Function

The MAX() function returns the largest value of the selected column.

Syntax:

SELECT MAX(column_name) FROM table_name;

Example:

select max(age) from student_details;

Output:

MAX( AGE)

25

SQL MIN() Function

The MIN() function returns the smallest value of the selected column.

Syntax:

SELECT MIN(column_name) FROM table_name;

Example:

select min(first_name) from student_details;

Output:

MIN(FIRST_NAME)

Akhilesh

SQL SUM() Function

The SUM() function returns the total sum of a numeric column.

Syntax:

SELECT SUM(column_name) FROM table_name;

Example:

Select sum(age)FROM student_details;

Output:

SUM( AGE)

99

SQL GROUP BY Clause

The SQL GROUP BY Clause is used along with the group functions to retrieve data grouped

according to one or more columns.

Syntax:

SELECT column_name, aggregate_function(column_name)

FROM table_name

WHERE column_name operator value

GROUP BY column_name;

Example:

select first_name, last_name, sum (age)

from student_details

group by first_name, last_name;

Output:

FIRST_NAME LAST_NAME SUM( AGE)

Akhilesh Kumar 25

Pravesh Shrivastava 24

Priyanka Ghosh 25

Nitin singh 25

SQL HAVING Clause

Having clause is used to filter data based on the group functions. This is similar to WHERE

condition but is used with group functions. Group functions cannot be used in WHERE Clause

but can be used in HAVING clause.

Syntax:

SELECT column_name, aggregate_function(column_name)

FROM table_name

WHERE column_name operator value

GROUP BY column_name

HAVING aggregate_function(column_name) operator value;

Example:

select first_name, sum (age)

from student_details

group BY first_name

having sum(age)> 20;

Output:

FIRST_NAME SUM( AGE)

Priyanka 25

Nitin 25

Akhilesh 25

Pravesh 24

SQL UPPER() Function

The UPPER() function converts the value of a field to uppercase.

Syntax:

SELECT UPPER(column_name) FROM table_name;

Example:

select upper(last_name) from student_details;

Output:

UPPER(LAST_NAME)

SHRIVASTAVA

GHOSH

SINGH

KUMAR

SQL LOWER() Function

The LOWER() function converts the value of a field to lowercase.

Syntax:

SELECT LOWER(column_name) FROM table_name;

Example:

select lower(last_name) from student_details;

Output:

LOWER(LAST_NAME)

shrivastava

ghosh

singh

kumar

SQL LENGTH() Function

The LENGTH() function returns the length of the value in a text field.

Syntax:

SELECT LENGTH(column_name) FROM table_name;

Example:

select length(first_name) from student_details;

Output:

LENGTH(FIRST_NAME)

20

20

20

20

SQL ROUND() Function

The ROUND() function is used to round a numeric field to the number of decimals specified.

Syntax:

SELECT ROUND(column_name,decimals) FROM table_name;

Parameter Description

column_name Required. The field to round.

Decimals Required. Specifies the number of decimals to be returned.

Example:

select first_name, round(age,0) from student_details;

Output:

FIRST_NAME ROUND( AGE,0)

Pravesh 24

Priyanka 25

Nitin 25

Akhilesh 25

SQL EXISTS Condition

The EXISTS condition is considered "to be met" if the subquery returns at least one row.

Syntax:

SELECT columns

FROM tables

WHERE EXISTS ( subquery );

The EXISTS condition can be used in any valid SQL statement - select, insert, update, or delete.

Table: student_details

ID S_F_NAME S_L_NAME S_SUB

1 Pravesh Shrivastava CSE

2 Nitin Singh CSE

3 Akhilesh Kumar CSE

4 Santosh Gupta Arts

5 Ranjita Kapoor BSC

Table: employee

E_ID E_NAME E_DEPT

1 Bindu HRM

2 Priyanka HRM

3 Abhishek Networking

Example:


where exists

(select * from employee

where student_details.id = employee.e_id);

Output:



2 Nitin Singh CSE


This select statement will return all records from the student_details table where there is at least

one record in the employee table with the same datatype.

Exists with Delete

Example:

delete from student_details

where exists



Output:




Exists with Update

Example:

update student_details

set s_f_name =( select e_name from employee

where student_details.id = employee.e_id)

where exists

(select e_name from employee

where employee.e_id = student_details.id);

Output:


1 Bindu Shrivastava CSE

2 Priyanka Singh CSE



not Exists Condition

Example:


where not exists


Where student_details.id = employee.e_id);

Output:




Not Exists with Delete

Example:

delete from student_details

where not exists



Output:



2 Nitin Singh CSE


Not Exists with Update Statement

Example:

update student_details

set s_f_name = (select e_name from employee

where student_details.id = employee.e_id)

where not exists

(select e_name from employee

where employee.e_id = student_details.id);

Output:



2 Nitin Singh CSE


4 - Gupta Arts

5 - Kapoor BSC

SQL INTERSECT Query

The INTERSECT query allows you to return the results of 2 or more "select" queries. However,

it only returns the rows selected by all queries. If a record exists in one query and not in the

other, it will be omitted from the INTERSECT results. Each SQL statement within the

INTERSECT query must have the same number of fields in the result sets with similar data

types.

Syntax:

SELECT field1, field2, . field_n

from TABLE1

INTERSECT


from TABLE2;

Example:

select supplier_id

from suppliers

intersect

select supplier_id

from orders;

Output:

Example: With ORDER BY Clause:

select supplier_id

from suppliers


intersect

select order_id

from orders


ORDER BY 1;

Output:

SUPPLIER_ID

1000

1001

1002

SUPPLIER_ID

1001

SQL MINUS Query

The MINUS query returns all rows in the first query that are not returned in the second query.

Each SQL statement within the MINUS query must have the same number of fields in the result

sets with similar data types.

Syntax:


FROM table1

MINUS


FROM tables2;

Example:

select supplier_id from suppliers

minus

select supplier_id from orders;

Output:

no data found

Example: With ORDER BY Clause:

select supplier_id

from suppliers


minus

select order_id

from orders


order by 1;

Output:

GRANT & REVOKE COMMNDS

DCL commands are used to enforce database security in a multiple user database environment.

Two types of DCL commands are GRANT and REVOKE. Only Database Administrator or

owner of the database object can provide/remove privileges on a database object.

SUPPLIER_ID

1002

SQL GRANT Command

SQL GRANT is a command used to provide access or privileges on the database objects to the

users.

Syntax:

GRANT privilege_name

ON object_name

TO {user_name |PUBLIC |role_name}

[WITH GRANT OPTION];

privilege_name is the access right or privilege granted to the user. Some of the

access rights are ALL, EXECUTE, and SELECT.

object_name is the name of an database object like TABLE, VIEW, STORED

PROC and SEQUENCE.

user_name is the name of the user to whom an access right is being granted.

user_name is the name of the user to whom an access right is being granted.

PUBLIC is used to grant access rights to all users.

ROLES are a set of privileges grouped together.

WITH GRANT OPTION allows a user to grant access rights to other users.

Example:

grant select on employee to user1;

This command grants a SELECT permission on employee table to user1. You should use

the WITH GRANT option carefully because for example if you GRANT SELECT privilege on

employee table to user1 using the WITH GRANT option, then user1 can GRANT SELECT

privilege on employee table to another user, such as user2 etc. Later, if you REVOKE the

SELECT privilege on employee from user1, still user2 will have SELECT privilege on employee

table.

SQL REVOKE Command

The REVOKE command removes user access rights or privileges to the database objects.

Syntax:

REVOKE privilege_name

ON object_name

FROM {user_name |PUBLIC |role_name};

Example:

REVOKE SELECT ON employee FROM user1;

This command will REVOKE a SELECT privilege on employee table from user1.

When you REVOKE SELECT privilege on a table from a user, the user will not be able to

SELECT data from that table anymore. However, if the user has received SELECT privileges

on that table from more than one users, he/she can SELECT from that table until everyone

who granted the permission revokes it. You cannot REVOKE privileges if they were not

initially granted by you.

Privileges and Roles

Privileges

Privileges define the access rights provided to a user on a database object.

There are two types of privileges:

1) System Privileges: This allows the user to CREATE, ALTER, or DROP database

objects.

2) Object Privileges: This allows the user to EXECUTE, SELECT, INSERT,

UPDATE, or DELETE data from database objects to which the privileges apply.

Few CREATE system privileges are listed below:

System Privileges Description

CREATE object allows users to create the specified

object in their own schema.

CREATE ANY

object

allows users to create the specified

object in any schema.

The above rules also apply for ALTER and DROP system privileges.

Few of the object privileges are listed below:

Object

Privileges Description

INSERT allows users to insert rows into a table.

SELECT allows users to select data from a

database object.

UPDATE allows user to update data in a table.

EXECUTE allows user to execute a stored procedure

or a function.

Roles

Roles are a collection of privileges or access rights. When there are many users in a

database it becomes difficult to grant or revoke privileges to users. Therefore, if you define

roles, you can grant or revoke privileges to users, thereby automatically granting or revoking

privileges. You can either create Roles or use the system roles pre-defined by oracle.

Some of the privileges granted to the system roles are as given below:

System

Role Privileges Granted to the Role

CONNECT

CREATE TABLE, CREATE VIEW,

CREATE SYNONYM, CREATE

SEQUENCE, CREATE SESSION etc.

RESOURCE

CREATE PROCEDURE, CREATE

SEQUENCE, CREATE TABLE,

CREATE TRIGGER etc. The primary

usage of the RESOURCE role is to

restrict access to database objects.

DBA ALL SYSTEM PRIVILEGES

Creating Roles:

Syntax:

CREATE ROLE role_name

[IDENTIFIED BY password];

Example:

To create a role called "tisting" with password as "pwd", the code will be as

follows:

create role testing

identified by pwd;

We can GRANT or REVOKE privilege to a role as below.

To grant CREATE TABLE privilege to a user by creating a testing role: First, create a testing Role:

create role testing;

Second, grant a CREATE TABLE privilege to the ROLE testing. You can add

more privileges to the ROLE.

grant create table to testing;

Third, grant the role to a user.

Create the user:

create user user1

identified by pwd;

Grant the Role:

grant testing to user1;

To revoke a CREATE TABLE privilege from testing ROLE, you can write:

revoke create table from testing;

Syntax to drop a role from the database:

DROP ROLE role_name;

Example:

drop role testing;

Oracle Built in Functions

There are two types of functions in Oracle.

1) Single Row Functions: Single row or Scalar functions return a value for every row that

is processed in a query.

2) Group Functions: These functions group the rows of data based on the values returned

by the query. This is discussed in SQL GROUP Functions.

There are four types of single row functions. They are:

1) Numeric Functions: These are functions that accept numeric input and return

numeric values.

2) Character or Text Functions: These are functions that accept character input

and can return both character and number values.

3) Date Functions: These are functions that take values that are of datatype DATE

as input and return values of datatype DATE, except for the

MONTHS_BETWEEN function, which returns a number.

4) Conversion Functions: These are functions that help us to convert a value in

one form to another form. For Example: a null value into an actual value, or a value

from one datatype to another datatype like NVL, TO_CHAR, TO_NUMBER,

TO_DATE etc.

What is a DUAL Table in Oracle?

This is a single row and single column dummy table provided by oracle. This is

used to perform mathematical calculations without using a table.

Example:

select * from dual; Output:

Example:

select 777 * 888 from dual;

Output:

Table: netlink

DUMMY

X

777*888

689976

E_ID E_SALARY E_NAME EMP_CITY

3 10000 Pravesh Bhopal

4 8000 Abhishek Bhopal

5 8000 SONAM Indore

1 18000.5 Nitin Gurgaon

2 18000 Akhilesh Gurgaon

6 8000 Jyotsana Mishra Indore

1) Numeric Functions:

Numeric functions are used to perform operations on numbers. They accept numeric values

as input and return numeric values as output.

Function Name Return Value

ABS (x) Absolute value of the number 'x'.

CEIL (x) Integer value that is Greater than or equal to the number 'x'.

FLOOR (x) Integer value that is Less than or equal to the number 'x'.

TRUNC (x, y) Truncates value of number 'x' up to 'y' decimal places.

ROUND (x, y) Rounded off value of the number 'x' up to the number 'y' decimal places.

select abs(e_salary) from netlink;

Output:

ABS(E_SALARY)

10000

8000

select ceil(e_salary) from netlink;

Output:

select floor(e_salary) from netlink;

Output:

FLOOR(E_SALARY)

10000

8000

18000

18000

select trunc(e_salary,3) from netlink;

Output:

18000.5

18000

CEIL(E_SALARY)

10000

8000

18001

18000

TRUNC(E_SALARY,3)

10000

8000

18000.5

18000

Character or Text Functions

Character or text functions are used to manipulate text strings. They accept strings or

characters as input and can return both character and number values as output.


INITCAP (string_value) All the letters in 'string_value' is converted to mixed case.

LTRIM (string_value,

trim_text)

All occurrences of 'trim_text' is removed from the left

of 'string_value'.

RTRIM (string_value,

trim_text)

All occurrences of 'trim_text' is removed from the right

of'string_value' .

TRIM (trim_text FROM

string_value)

All occurrences of 'trim_text' from the left and right

of 'string_value' ,'trim_text' can also be only one character long .

SUBSTR (string_value,

m, n)

Returns 'n' number of characters from'string_value' starting from the

'm'position.

LENGTH (string_value) Number of characters in 'string_value'in returned.

LPAD (string_value, n,

pad_value)

Returns 'string_value' left-padded with'pad_value' . The length of the

whole string will be of 'n' characters.

RPAD (string_value, n,

pad_value)

Returns 'string_value' right-padded with 'pad_value' . The length of

the whole string will be of 'n' characters.

select initcap('Pravesh') from netlink;

Output:

INITCAP( 'PRAVESH')

Pravesh

Pravesh

Pravesh

Pravesh

Pravesh

Pravesh

select ltrim('Good Morning', 'Good') from emp;

Output:

LTRIM('GOODMORNING', 'GOOD')

Morning

select rtrim('Good Morning', 'Morning') from emp;

Output:

RTRIM('GOODMORNING', 'MORNING')

Good

select trim('G' from 'Good Morning') from emp;

Output:

TRIM('G'FROM'GOODMORNING')

ood Morning

select substr('Good Morning', 6, 6) from emp;

Output:

select length('Good Morning') from emp;

Output:

SUBSTR( 'GOODMORNING',6,6)

Mornin

LENGTH( 'GOODMORNING')

12

select lpad('Good',6,'*') from emp;

Output:

LPAD('GOOD',6, '* ')

**Good

select rpad('Good',9,'*') from emp;

Output:

3) Date Functions

These are functions that take values that are of datatype DATE as input and return values of

datatypes DATE, except for the MONTHS_BETWEEN function, which returns a number as

output.


ADD_MONTHS (date, n) Returns a date value after adding 'n'months to the date 'x'.

MONTHS_BETWEEN (x1,

x2) Returns the number of months between dates x1 and x2.

NEXT_DAY (x, week_day) Returns the next date of the 'week_day'on or after the

date 'x' occurs.

LAST_DAY (x) It is used to determine the number of days remaining in a month

from the date 'x' specified.

SYSDATE Returns the systems current date and time.

NEW_TIME (x, zone1,

zone2)

Returns the date and time in zone2 if date 'x' represents the time

in zone1.

select add_months('7-oct-2010',3) from emp;

RPAD('GOOD',9, '* ')

Good*****

Output:

ADD_MONTHS( '7-OCT-2010',3)

07-JAN-11

select months_between('7-oct-2010','7-dec-2010') from emp;

Output:

MONTHS_BETWEEN('7-OCT-2010', '7-DEC-2010')

-2

select next_day ('7-oct-2010','Wednesday') from emp;

Output:

NEXT_DAY('7-OCT-2010', 'WEDNESDAY')

13-OCT-10

select last_day('7-oct-2010') from emp;

Output:

LAST_DAY('7-OCT-2010')

31-OCT-10

select new_time('7-oct-2010','gmt','est') from emp;

Output:

NEW_TIME('7-OCT-2010', 'GMT', 'EST')

06-OCT-10

3) Conversion Functions

These are functions that help us to convert a value in one form to another form. For Ex: a

null value into an actual value, or a value from one datatype to another datatype like NVL,

TO_CHAR, TO_NUMBER, TO_DATE.


TO_CHAR (x [,y]) Converts Numeric and Date values to a character string value. It cannot

be used for calculations since it is a string value.

TO_DATE (x ,[

date_format])

Converts a valid Numeric and Character values to a Date value. Date is

formatted to the format specified by 'date_format'.

NVL (x, y) If 'x' is NULL, replace it with 'y'. 'x' and 'y'must be of the same datatype.

select to_char(3000,'$9999') from emp;

Output:

select to_char(sysdate,'day,month yyyy') from emp;

TO_CHAR(3000, '$9999')

$3000

Output:

select to_date('01-Jun-2010') from emp;

Output:

select nvl(null,1) from emp;

Output:

Note:

Query to get the number of columns in a table:

select COUNT(*) from dba_tab_columns

where table_name = 'EMPLOYEE';

table_name should be in capital letters.

TO_CHAR(SYSDATE, 'DAY,MONTHYYYY')

friday ,october 2010

TO_DATE( '01-JUN-2010')

01-JUN-10

NVL(NULL,1)

1

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