Single-Row Functions

Single-Row FunctionsSingle-Row FunctionsSingle-Row FunctionsSingle-Row Functions

SQL FunctionsSQL FunctionsSQL FunctionsSQL Functions

FunctionFunctionInputInput

arg 1arg 1

arg 2arg 2

arg arg nn

Function Function performs actionperforms action

OutputOutput

ResultResultvaluevalue

Two Types of SQL FunctionsTwo Types of SQL FunctionsTwo Types of SQL FunctionsTwo Types of SQL Functions

FunctionsFunctions

Single-row Single-row functionsfunctions

Multiple-rowMultiple-rowfunctionsfunctions


– Manipulate data items– Accept arguments and return one

value– May modify the data type– Can be nested

– Manipulate data items– Accept arguments and return one

value– May modify the data type– Can be nested

function_name (column|expression, [arg1, arg2,...])function_name (column|expression, [arg1, arg2,...])


ConversionConversion

CharacterCharacter NumberNumber

DateDate

Single-row Single-row functionsfunctions

Character FunctionsCharacter FunctionsCharacter FunctionsCharacter Functions

CharacterCharacterfunctionsfunctions

LOWERLOWER

UPPERUPPER

SUBSTRINGSUBSTRING

LENLEN

LTRIMLTRIM

RTRIMRTRIM

LEFTLEFT

RIGHTRIGHT

Case conversion Case conversion functionsfunctions

Character manipulationCharacter manipulationfunctionsfunctions

Function Result

Case Conversion FunctionsCase Conversion FunctionsCase Conversion FunctionsCase Conversion Functions

Convert case for character stringsConvert case for character strings

LOWER('SQL Course')

UPPER('SQL Course')

sql course

SQL COURSE

Using Case Conversion Using Case Conversion FunctionsFunctions

Using Case Conversion Using Case Conversion FunctionsFunctions

Display the employee number, name, and department number for employee Blake.

Display the employee number, name, and department number for employee Blake.

SELECT empno, ename, deptno FROM emp WHERE ename = 'blake' no rows selectedno rows selected

SELECT empno, ename, deptno FROM emp WHERE ename = 'blake' no rows selectedno rows selected

EMPNO ENAME DEPTNO--------- ---------- --------- 7698 BLAKE 30

EMPNO ENAME DEPTNO--------- ---------- --------- 7698 BLAKE 30

SELECT empno, ename, deptno FROM emp WHERE LOWER(ename) = 'blake'

SUBSTRING('String',1,3)

LEN(‘String’)

LTRIM(‘ String ’)

RTRIM(‘ String ’)

LEFT(‘String’, 3)

RIGHT(‘String’, 3)

Str

6

String

String

Str

ing

Function Result

Character Manipulation Character Manipulation FunctionsFunctions

Character Manipulation Character Manipulation FunctionsFunctions

Manipulate character stringsManipulate character strings

Using the Character Using the Character Manipulation FunctionsManipulation Functions

Using the Character Using the Character Manipulation FunctionsManipulation Functions

SELECT SUBSTRING('String',1,3) substr,LEN('String') Lenstr, RTRIM(' string ') Rtrimstr, LTRIM(' string ') Ltrimstr,LEFT('String',3) Leftstr,RIGHT('String',3) Rightstr

Using the ROUND FunctionUsing the ROUND FunctionUsing the ROUND FunctionUsing the ROUND Function

SELECT ROUND(45.923,2), ROUND(45.923,0), ROUND(45.923,-1)

ROUND(45.923,2) ROUND(45.923,0) ROUND(45.923,-1)--------------- -------------- ----------------- 45.92 46 50

SELECT FLOOR(123.45), FLOOR(-123.45), FLOOR(123.95)

Using the FLOOR,CEILING Using the FLOOR,CEILING FunctionsFunctions

Using the FLOOR,CEILING Using the FLOOR,CEILING FunctionsFunctions

SELECT CEILING(123.45), CEILING(-123.45), CEILING(0.0)

Aggregating Data Aggregating Data Using Group FunctionsUsing Group Functions

Aggregating Data Aggregating Data Using Group FunctionsUsing Group Functions

What Are Group Functions?What Are Group Functions?What Are Group Functions?What Are Group Functions? Group functions operate on sets of rows to

give one result per group. Group functions operate on sets of rows to

give one result per group.EMPEMP

““maximum maximum salary in salary in

the EMP table”the EMP table”

DEPTNO SAL--------- --------- 10 2450 10 5000 10 1300 20 800 20 1100 20 3000 20 3000 20 2975 30 1600 30 2850 30 1250 30 950 30 1500 30 1250

MAX(SAL)

---------

5000

Types of Group FunctionsTypes of Group FunctionsTypes of Group FunctionsTypes of Group Functions

– AVG – COUNT – MAX– MIN – SUM

– AVG – COUNT – MAX– MIN – SUM

Using Group FunctionsUsing Group FunctionsUsing Group FunctionsUsing Group Functions

SELECT [column,] group_function(column)FROM table[WHERE condition][GROUP BY column][ORDER BY column]

Using AVG and SUM Using AVG and SUM FunctionsFunctions

Using AVG and SUM Using AVG and SUM FunctionsFunctions

AVG(SAL) MAX(SAL) MIN(SAL) SUM(SAL)-------- --------- --------- --------- 1400 1600 1250 5600

You can use AVG and SUM for numeric data.You can use AVG and SUM for numeric data.

SELECT AVG(sal), MAX(sal),MIN(sal), SUM(sal)

FROM empWHERE job LIKE 'SALES%'

Using MIN and MAX Using MIN and MAX FunctionsFunctions

Using MIN and MAX Using MIN and MAX FunctionsFunctions

You can use MIN and MAX for any datatype.

You can use MIN and MAX for any datatype.

SELECT MIN(hiredate), MAX(hiredate)FROM emp

MIN(HIRED MAX(HIRED--------- ---------17-DEC-80 12-JAN-83

Using the COUNT FunctionUsing the COUNT FunctionUsing the COUNT FunctionUsing the COUNT Function

COUNT(*)--------- 6

SELECT COUNT(*)FROM empWHERE deptno = 30

COUNT(*) returns the number of rows in a table.

COUNT(*) returns the number of rows in a table.

Using the COUNT FunctionUsing the COUNT FunctionUsing the COUNT FunctionUsing the COUNT Function

COUNT(expr) returns the number of nonnull rows.

COUNT(expr) returns the number of nonnull rows.

SELECT COUNT(comm)FROM empWHERE deptno = 30

COUNT(COMM)----------- 4

Group Functions and Null Group Functions and Null ValuesValues

Group Functions and Null Group Functions and Null ValuesValues

Group functions ignore null values in the column.

Group functions ignore null values in the column.

SELECT AVG(comm)FROM emp

AVG(COMM)--------- 550

Using the ISNULL Function Using the ISNULL Function with Group Functionswith Group Functions

Using the ISNULL Function Using the ISNULL Function with Group Functionswith Group Functions

The ISNULL function forces group functions to include null values.

The ISNULL function forces group functions to include null values.

SELECT AVG(ISNULL(comm,0)) COMMISSION FROM emp

COMMISSION---------- 157.14286

Creating Groups of Data Creating Groups of Data Creating Groups of Data Creating Groups of Data EMPEMP

““averageaveragesalary salary in EMPin EMPtable table

for each for each department”department”

2916.66672916.6667

21752175

1566.66671566.6667

DEPTNO SAL--------- --------- 10 2450 10 5000 10 1300 20 800 20 1100 20 3000 20 3000 20 2975 30 1600 30 2850 30 1250 30 950 30 1500 30 1250

DEPTNO AVG(SAL)

------- ---------

10 2916.6667

20 2175

30 1566.6667

Creating Groups of Data: Creating Groups of Data: GROUP BY ClauseGROUP BY Clause

Creating Groups of Data: Creating Groups of Data: GROUP BY ClauseGROUP BY Clause

SELECT column, group_function(column)FROM table[WHERE condition][GROUP BY group_by_expression][ORDER BY column]

Divide rows in a table into smaller groups by using the GROUP BY clause.

Divide rows in a table into smaller groups by using the GROUP BY clause.

Using the GROUP BY Clause Using the GROUP BY Clause Using the GROUP BY Clause Using the GROUP BY Clause All columns in the SELECT list that are

not in group functions must be in the GROUP BY clause.

All columns in the SELECT list that are not in group functions must be in the GROUP BY clause.

SELECT deptno, AVG(sal)FROM empGROUP BY deptno

DEPTNO AVG(SAL)--------- --------- 10 2916.6667 20 2175 30 1566.6667

Using the GROUP BY Clause Using the GROUP BY Clause Using the GROUP BY Clause Using the GROUP BY Clause The GROUP BY column does not have

to be in the SELECT list.

The GROUP BY column does not have to be in the SELECT list.

SELECT AVG(sal)FROM empGROUP BY deptno

AVG(SAL)--------- 2916.6667 21751566.6667

Grouping by More Grouping by More Than One ColumnThan One ColumnGrouping by More Grouping by More Than One ColumnThan One Column

EMPEMP

““sum salaries in sum salaries in the EMP tablethe EMP tablefor each job, for each job, grouped by grouped by department”department”

DEPTNO JOB SAL

--------- --------- ---------

10 MANAGER 2450

10 PRESIDENT 5000

10 CLERK 1300

20 CLERK 800

20 CLERK 1100

20 ANALYST 3000

20 ANALYST 3000

20 MANAGER 2975

30 SALESMAN 1600

30 MANAGER 2850

30 SALESMAN 1250

30 CLERK 950

30 SALESMAN 1500

30 SALESMAN 1250

JOB SUM(SAL)

--------- ---------

CLERK 1300

MANAGER 2450

PRESIDENT 5000

ANALYST 6000

CLERK 1900

MANAGER 2975

CLERK 950

MANAGER 2850

SALESMAN 5600

DEPTNO

--------

10

10

10

20

20

20

30

30

30

Using the GROUP BY Clause Using the GROUP BY Clause on Multiple Columnson Multiple Columns

Using the GROUP BY Clause Using the GROUP BY Clause on Multiple Columnson Multiple Columns

SELECT deptno, job, sum(sal)FROM empGROUP BY deptno, job

DEPTNO JOB SUM(SAL)--------- --------- --------- 10 CLERK 1300 10 MANAGER 2450 10 PRESIDENT 5000 20 ANALYST 6000 20 CLERK 1900...9 rows selected.

Illegal Queries Illegal Queries Using Group FunctionsUsing Group Functions


Any column or expression in the SELECT list that is not an aggregate function must be in the GROUP BY clause.

Any column or expression in the SELECT list that is not an aggregate function must be in the GROUP BY clause.SELECT deptno, COUNT(ename)FROM emp

SELECT deptno, COUNT(ename)FROM emp

Server: Msg 8118, Level 16, State 1, Line 1 Column 'emp.DEPTNO' is invalid in the select list because it is not contained in an aggregate function

and there is no GROUP BY clause.

Server: Msg 8118, Level 16, State 1, Line 1 Column 'emp.DEPTNO' is invalid in the select list because it is not contained in an aggregate function

and there is no GROUP BY clause.

Column missing in the GROUP BY clause






– You cannot use the WHERE clause to restrict groups.

– You use the HAVING clause to restrict groups.

– You cannot use the WHERE clause to restrict groups.

– You use the HAVING clause to restrict groups.

SELECT deptno, AVG(sal)FROM empWHERE AVG(sal) > 2000GROUP BY deptno

SELECT deptno, AVG(sal)FROM empWHERE AVG(sal) > 2000GROUP BY deptno

Server: Msg 147, Level 15, State 1, Line 3An aggregate may not appear in the WHERE clause

unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated

is an outer reference.

Server: Msg 147, Level 15, State 1, Line 3An aggregate may not appear in the WHERE clause

unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated

is an outer reference.

Cannot use the WHERE clause


to

restrict groups

to restrict groups



to

restrict groups

to restrict groups

Excluding Group ResultsExcluding Group ResultsExcluding Group ResultsExcluding Group Results

““maximummaximumsalarysalary

per departmentper departmentgreater thangreater than

$2900”$2900”

EMPEMP

50005000

30003000

28502850

DEPTNO SAL

--------- ---------

10 2450

10 5000

10 1300

20 800

20 1100

20 3000

20 3000

20 2975

30 1600

30 2850

30 1250

30 950

30 1500

30 1250

DEPTNO MAX(SAL)

--------- ---------

10 5000

20 3000

Excluding Group Results: Excluding Group Results: HAVING ClauseHAVING Clause

Excluding Group Results: Excluding Group Results: HAVING ClauseHAVING Clause

Use the HAVING clause to restrict groups

Rows are grouped. The group function is applied. Groups matching the HAVING clause are

displayed.

Use the HAVING clause to restrict groups

Rows are grouped. The group function is applied. Groups matching the HAVING clause are

displayed.SELECT column, group_functionFROM table[WHERE condition][GROUP BY group_by_expression][HAVING group_condition][ORDER BY column]

Using the HAVING ClauseUsing the HAVING ClauseUsing the HAVING ClauseUsing the HAVING Clause

SELECT deptno, max(sal)FROM empGROUP BY deptnoHAVING max(sal)>2900

DEPTNO MAX(SAL)--------- --------- 10 5000 20 3000

Using the HAVING ClauseUsing the HAVING ClauseUsing the HAVING ClauseUsing the HAVING Clause

SELECT job, SUM(sal) PAYROLLFROM empWHERE job NOT LIKE 'SALES%'GROUP BY jobHAVING SUM(sal)>5000ORDER BY SUM(sal)

JOB PAYROLL--------- ---------ANALYST 6000MANAGER 8275

Nesting Group FunctionsNesting Group FunctionsNesting Group FunctionsNesting Group Functions

SELECT max(avg(sal))FROM empGROUP BY deptno

MAX(AVG(SAL))------------- 2916.6667

Display the maximum average salary. Display the maximum average salary.

SummarySummarySummarySummarySELECT column, group_function(column)FROM table[WHERE condition][GROUP BY group_by_expression][HAVING group_condition][ORDER BY column]

Order of evaluation of the clauses:– WHERE clause– GROUP BY clause– HAVING clause

Order of evaluation of the clauses:– WHERE clause– GROUP BY clause– HAVING clause

Displaying Data Displaying Data from Multiple Tablesfrom Multiple Tables

Displaying Data Displaying Data from Multiple Tablesfrom Multiple Tables

ObjectivesObjectivesObjectivesObjectives

After completing this lesson, you should be able to do the following:– Write SELECT statements to access data

from more than one table using equality and nonequality joins

– View data that generally does not meet a join condition by using outer joins

– Join a table to itself

After completing this lesson, you should be able to do the following:– Write SELECT statements to access data

from more than one table using equality and nonequality joins

– View data that generally does not meet a join condition by using outer joins

– Join a table to itself

EMPNO DEPTNO LOC----- ------- -------- 7839 10 NEW YORK 7698 30 CHICAGO 7782 10 NEW YORK 7566 20 DALLAS 7654 30 CHICAGO 7499 30 CHICAGO...14 rows selected.

EMPNO DEPTNO LOC----- ------- -------- 7839 10 NEW YORK 7698 30 CHICAGO 7782 10 NEW YORK 7566 20 DALLAS 7654 30 CHICAGO 7499 30 CHICAGO...14 rows selected.

Obtaining Data from Multiple TablesObtaining Data from Multiple TablesObtaining Data from Multiple TablesObtaining Data from Multiple TablesEMP EMP DEPT DEPT EMPNO ENAME ... DEPTNO------ ----- ... ------ 7839 KING ... 10 7698 BLAKE ... 30 ... 7934 MILLER ... 10

DEPTNO DNAME LOC ------ ---------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

What Is a Join?What Is a Join?What Is a Join?What Is a Join?Use a join to query data from more than one table.

– Write the join condition in the WHERE clause.

– Prefix the column name with the table name when the same column name appears in more than one table.

Use a join to query data from more than one table.

– Write the join condition in the WHERE clause.

– Prefix the column name with the table name when the same column name appears in more than one table.

SELECT table1.column, table2.columnFROM table1, table2WHERE table1.column1 = table2.column2

SELECT table1.column, table2.columnFROM table1, table2WHERE table1.column1 = table2.column2

Cartesian ProductCartesian ProductCartesian ProductCartesian Product

– A Cartesian product is formed when: A join condition is omitted A join condition is invalid All rows in the first table are joined to all rows in

the second table

– To avoid a Cartesian product, always include a valid join condition in a WHERE clause.

– A Cartesian product is formed when: A join condition is omitted A join condition is invalid All rows in the first table are joined to all rows in

the second table

– To avoid a Cartesian product, always include a valid join condition in a WHERE clause.

Generating a Cartesian Generating a Cartesian ProductProduct

Generating a Cartesian Generating a Cartesian ProductProduct

ENAME DNAME------ ----------KING ACCOUNTINGBLAKE ACCOUNTING ...KING RESEARCHBLAKE RESEARCH...56 rows selected.

ENAME DNAME------ ----------KING ACCOUNTINGBLAKE ACCOUNTING ...KING RESEARCHBLAKE RESEARCH...56 rows selected.

EMP (14 rows) EMP (14 rows) DEPT (4 rows) DEPT (4 rows)

EMPNO ENAME ... DEPTNO------ ----- ... ------ 7839 KING ... 10 7698 BLAKE ... 30 ... 7934 MILLER ... 10

EMPNO ENAME ... DEPTNO------ ----- ... ------ 7839 KING ... 10 7698 BLAKE ... 30 ... 7934 MILLER ... 10



““CartesianCartesianproduct: product:

14*4=56 rows”14*4=56 rows”

Types of JoinsTypes of JoinsTypes of JoinsTypes of Joins

EquijoinEquijoin Non-equijoinNon-equijoin Outer joinOuter join Self joinSelf join

What Is an Equijoin?What Is an Equijoin?What Is an Equijoin?What Is an Equijoin?EMP EMP DEPT DEPT EMPNO ENAME DEPTNO------ ------- ------- 7839 KING 10 7698 BLAKE 30 7782 CLARK 10 7566 JONES 20 7654 MARTIN 30 7499 ALLEN 30 7844 TURNER 30 7900 JAMES 30 7521 WARD 30 7902 FORD 20 7369 SMITH 20...14 rows selected.

DEPTNO DNAME LOC ------- ---------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

4 rows selected.

Foreign keyForeign key Primary keyPrimary key

Retrieving Records Retrieving Records with Equijoinswith Equijoins

Retrieving Records Retrieving Records with Equijoinswith Equijoins

SELECT emp.empno, emp.ename, emp.deptno, dept.deptno, dept.loc FROM emp, dept WHERE emp.deptno=dept.deptno

EMPNO ENAME DEPTNO DEPTNO LOC----- ------ ------ ------ --------- 7839 KING 10 10 NEW YORK 7698 BLAKE 30 30 CHICAGO 7782 CLARK 10 10 NEW YORK 7566 JONES 20 20 DALLAS...14 rows selected.

Non-EquijoinsNon-EquijoinsNon-EquijoinsNon-EquijoinsEMPEMP SALGRADESALGRADE

““salary in the EMP salary in the EMP table is between table is between low salary and high low salary and high salary in the SALGRADEsalary in the SALGRADEtable”table”

EMPNO ENAME SAL------ ------- ------ 7839 KING 5000 7698 BLAKE 2850 7782 CLARK 2450 7566 JONES 2975 7654 MARTIN 1250 7499 ALLEN 1600 7844 TURNER 1500 7900 JAMES 950...14 rows selected.

GRADE LOSAL HISAL----- ----- ------1 700 12002 1201 14003 1401 20004 2001 30005 3001 9999

Retrieving Records Retrieving Records with Non-Equijoinswith Non-Equijoins

Retrieving Records Retrieving Records with Non-Equijoinswith Non-Equijoins

ENAME SAL GRADE---------- --------- ---------JAMES 950 1SMITH 800 1ADAMS 1100 1...14 rows selected.

SELECT e.ename, e.sal, s.grade

FROM emp e, salgrade s

WHERE e.sal

BETWEEN s.losal AND s.hisal

Types of Join Types of Join

1. Inner Join

2. Outer Join

3. Self Join

Inner JoinInner Join

In this type of join, Records in the joined tables must have the same value for fields that are joined.

For example List the employees who work in

‘ACCOUNTING’ department.

ExampleExample

SELECT ename, dname

FROM emp INNER JOIN dept

ON emp.deptno=dept.deptno

WHERE UPPER(dname)='ACCOUNTING'

OUTER JOINOUTER JOINIn this type of join, all records from one table are listed in the output even if no joining record is available in the joined table. Outer joins are categorized as left outer join and right outer join. For example, List all employees along with their department names or List all departments along with the employee names working in these departments.

Outer JoinsOuter JoinsOuter JoinsOuter Joins– You use an outer join to also see rows that

do not usually meet the join condition.– You use an outer join to also see rows that

do not usually meet the join condition.

SELECT table1.column, table2.column

FROM table1 LEFT OUTER JOIN table2

ON table1.column = table2.column


FROM table1 LEFT OUTER JOIN table2



FROM table1 RIGHT OUTER JOIN table2



FROM table1 RIGHT OUTER JOIN table2


Outer JoinsOuter JoinsOuter JoinsOuter Joins– Outer join operator is

Left outer (*=) Right outer (=*)

– Outer join operator is Left outer (*=) Right outer (=*)


FROM table1, table2

WHERE table1.column *= table2.column


FROM table1, table2

WHERE table1.column *= table2.column


FROM table1, table2

WHERE table1.column =* table2.column


FROM table1, table2

WHERE table1.column =* table2.column

Outer JoinsOuter JoinsOuter JoinsOuter JoinsEMP EMP DEPT DEPT

No employee in theNo employee in theOPERATIONS departmentOPERATIONS department

ENAME DEPTNO----- ------KING 10BLAKE 30CLARK 10JONES 20...

DEPTNO DNAME------ ----------10 ACCOUNTING20 RESEARCH...40 OPERATIONS

Using Outer JoinsUsing Outer JoinsUsing Outer JoinsUsing Outer JoinsSELECT e.ename, d.deptno, d.dname

FROM emp e LEFT OUTER JOIN dept d

ON e.deptno = d.deptno

ORDER BY e.deptno

ENAME DEPTNO DNAME---------- --------- -------------KING 10 ACCOUNTINGCLARK 10 ACCOUNTING... 40 OPERATIONS15 rows selected.

Example 1Example 1

SELECT e.ename, d.deptno, d.dnameFROM emp e LEFT OUTER JOIN dept d

ON e.deptno = d.deptnoORDER BY d.deptno

— OR—SELECT e.ename, d.deptno, d.dnameFROM emp e, dept dWHERE e.deptno *= d.deptnoORDER BY d.deptno

SELECT e.ename, d.deptno, d.dname

FROM emp e RIGHT OUTER JOIN dept d


ORDER BY d.deptno

— OR—


FROM emp e, dept d

WHERE e.deptno =* d.deptno

ORDER BY d.deptno

Example 2Example 2

Full Outer JoinFull Outer Join

FULL OUTER JOIN includes all rows from both tables, regardless of whether or not the other table has a matching value.

Full Outer JoinFull Outer Join


FROM emp e FULL OUTER JOIN dept d


ORDER BY d.deptno

Self JoinsSelf JoinsSelf JoinsSelf JoinsEMP (WORKER)EMP (WORKER) EMP (MANAGER)EMP (MANAGER)

““MGR in the WORKER table is equal to EMPNO in the MGR in the WORKER table is equal to EMPNO in the MANAGER table”MANAGER table”

EMPNO ENAME MGR----- ------ ---- 7839 KING 7698 BLAKE 7839 7782 CLARK 7839 7566 JONES 7839 7654 MARTIN 7698 7499 ALLEN 7698

EMPNO ENAME----- --------

7839 KING 7839 KING 7839 KING 7698 BLAKE 7698 BLAKE

Self JoinSelf Join

There are the times when joining of one table with itself is required. For example, suppose we have an employee’s table having manager’s ID also and we want to list the employee name with his manager name. Then we will require the usage of employee table twice. For such situations Self join is used as shown in the example.

ExampleExample

SELECT worker.ename + ' works for ' + manager.ename

FROM emp worker, emp manager

WHERE worker.mgr = manager.empno

Joining a Table to ItselfJoining a Table to ItselfJoining a Table to ItselfJoining a Table to Itself

-------------------------------BLAKE works for KINGCLARK works for KINGJONES works for KINGMARTIN works for BLAKE...13 rows selected.

-------------------------------BLAKE works for KINGCLARK works for KINGJONES works for KINGMARTIN works for BLAKE...13 rows selected.

SELECT worker.ename + ' works for ' + manager.enameFROM emp worker INNER JOIN emp manager

ON worker.mgr = manager.empno

Qualifying Ambiguous Qualifying Ambiguous Column NamesColumn Names

Qualifying Ambiguous Qualifying Ambiguous Column NamesColumn Names

– Use table prefixes to qualify column names that are in multiple tables.

– Improve performance by using table prefixes.

– Distinguish columns that have identical names but reside in different tables by using column aliases.

– Use table prefixes to qualify column names that are in multiple tables.

– Improve performance by using table prefixes.

– Distinguish columns that have identical names but reside in different tables by using column aliases.

Additional Search ConditionsAdditional Search ConditionsUsing the AND Operator Using the AND Operator

Additional Search ConditionsAdditional Search ConditionsUsing the AND Operator Using the AND Operator

EMP EMP DEPT DEPT EMPNO ENAME DEPTNO------ ------- ------- 7839 KING 10 7698 BLAKE 30 7782 CLARK 10 7566 JONES 20 7654 MARTIN 30 7499 ALLEN 30 7844 TURNER 30 7900 JAMES 30 7521 WARD 30 7902 FORD 20 7369 SMITH 20...14 rows selected.

DEPTNO DNAME LOC ------ --------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

4 rows selected.

Using Table AliasesUsing Table AliasesUsing Table AliasesUsing Table AliasesSimplify queries by using table aliases.Simplify queries by using table aliases. SELECT emp.empno, emp.ename, emp.deptno,

dept.deptno, dept.loc

FROM emp, dept

WHERE emp.deptno=dept.deptno;

SELECT e.empno, e.ename, e.deptno,

d.deptno, d.loc

FROM emp e, dept d

WHERE e.deptno=d.deptno;

Joining More Than Two Joining More Than Two TablesTables

Joining More Than Two Joining More Than Two TablesTables

NAME CUSTID----------- ------JOCKSPORTS 100TKB SPORT SHOP 101VOLLYRITE 102JUST TENNIS 103K+T SPORTS 105SHAPE UP 106WOMENS SPORTS 107... ...9 rows selected.

NAME CUSTID----------- ------JOCKSPORTS 100TKB SPORT SHOP 101VOLLYRITE 102JUST TENNIS 103K+T SPORTS 105SHAPE UP 106WOMENS SPORTS 107... ...9 rows selected.

CUSTOMER CUSTOMER

CUSTID ORDID------- ------- 101 610 102 611 104 612 106 601 102 602 106 604 106 605... 21 rows selected.

CUSTID ORDID------- ------- 101 610 102 611 104 612 106 601 102 602 106 604 106 605... 21 rows selected.

ORD ORD

ORDID ITEMID------ ------- 610 3 611 1 612 1 601 1 602 1...64 rows selected.

ORDID ITEMID------ ------- 610 3 611 1 612 1 601 1 602 1...64 rows selected.

ITEM ITEM

SummarySummarySummarySummary

EquijoinEquijoin Non-equijoinNon-equijoin Outer joinOuter join Self joinSelf join

SELECT table1.column, table2.columnFROM table1, table2WHERE table1.column1 = table2.column2;

SELECT table1.column, table2.columnFROM table1, table2WHERE table1.column1 = table2.column2;

This predicate is used to limit the output to the top most n records only, Where n must be an integer.

For Example

SELECT top 3 deptno, ename

FROM emp

Top nTop nTop nTop n

SubqueriesSubqueriesSubqueriesSubqueries

ObjectivesObjectivesObjectivesObjectives

After completing this lesson, you should be able to do the following:– Describe the types of problems that

subqueries can solve– Define subqueries– List the types of subqueries– Write single-row and multiple-row

subqueries

After completing this lesson, you should be able to do the following:– Describe the types of problems that

subqueries can solve– Define subqueries– List the types of subqueries– Write single-row and multiple-row

subqueries

Using a Subquery Using a Subquery to Solve a Problemto Solve a ProblemUsing a Subquery Using a Subquery to Solve a Problemto Solve a Problem

“Who has a salary greater than Jones’?” “Who has a salary greater than Jones’?”

“Which employees have a salary greater than Jones’ salary?”

Main Query

??

“What is Jones’ salary?”??

Subquery

SubqueriesSubqueriesSubqueriesSubqueries

– The subquery (inner query) executes once before the main query.– The result of the subquery is used by the main query (outer query).

– The subquery (inner query) executes once before the main query.– The result of the subquery is used by the main query (outer query).

SELECT select_listFROM tableWHERE expr operator

(SELECT select_list FROM table)

2975

SELECT ename FROM emp WHERE sal > (SELECT sal FROM emp WHERE empno=7566)

Using a SubqueryUsing a SubqueryUsing a SubqueryUsing a Subquery

ENAME----------KINGFORDSCOTT

ENAME----------KINGFORDSCOTT

Guidelines for Using Guidelines for Using SubqueriesSubqueries

Guidelines for Using Guidelines for Using SubqueriesSubqueries

– Enclose subqueries in parentheses. – Place subqueries on the right side of the

comparison operator.– Do not add an ORDER BY clause to a

subquery.– Use single-row operators with single-row

subqueries.– Use multiple-row operators with multiple-

row subqueries.

– Enclose subqueries in parentheses. – Place subqueries on the right side of the

comparison operator.– Do not add an ORDER BY clause to a

subquery.– Use single-row operators with single-row

subqueries.– Use multiple-row operators with multiple-

row subqueries.

Types of SubqueriesTypes of SubqueriesTypes of SubqueriesTypes of Subqueries– Single-row subquery– Single-row subquery

Main query

Subquery returnsreturns

CLERKCLERK

• Multiple-row subquery• Multiple-row subquery

CLERKCLERKMANAGERMANAGER

Main query


• Multiple-column subquery• Multiple-column subquery

CLERK 7900CLERK 7900MANAGER 7698MANAGER 7698

Main query


Single-Row SubqueriesSingle-Row SubqueriesSingle-Row SubqueriesSingle-Row Subqueries– Return only one row– Use single-row comparison operators

– Return only one row– Use single-row comparison operators

Operator

=

>

>=

<

<=

<>

Meaning

Equal to

Greater than

Greater than or equal to

Less than

Less than or equal to

Not equal to

Executing Single-Row Executing Single-Row SubqueriesSubqueries

Executing Single-Row Executing Single-Row SubqueriesSubqueries

CLERK

1100

ENAME JOB---------- ---------MILLER CLERK

ENAME JOB---------- ---------MILLER CLERK

SELECT ename, job FROM emp WHERE job = (SELECT job FROM emp WHERE empno = 7369) AND sal > (SELECT sal FROM emp WHERE empno = 7876)

Using Group Functions Using Group Functions in a Subqueryin a Subquery

Using Group Functions Using Group Functions in a Subqueryin a Subquery

800

ENAME JOB SAL---------- --------- ---------SMITH CLERK 800

ENAME JOB SAL---------- --------- ---------SMITH CLERK 800

SELECT ename, job, sal FROM emp WHERE sal = (SELECT MIN(sal) FROM emp)

HAVING Clause with HAVING Clause with SubqueriesSubqueries

HAVING Clause with HAVING Clause with SubqueriesSubqueries

– Subqueries are executed first.– Results are returned into the HAVING

clause of the main query.

– Subqueries are executed first.– Results are returned into the HAVING

clause of the main query.

800

SELECT deptno, MIN(sal) FROM emp GROUP BY deptno HAVING MIN(sal) > (SELECT MIN(sal) FROM emp WHERE deptno = 20)

What Is Wrong What Is Wrong with This Statement?with This Statement?

What Is Wrong What Is Wrong with This Statement?with This Statement?

Server: Msg 512, Level 16, State 1, Line 1 Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or

when the subquery is used as an expression.

Server: Msg 512, Level 16, State 1, Line 1 Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or

when the subquery is used as an expression.

SELECT empno, ename FROM emp WHERE sal = (SELECT MIN(sal) FROM emp GROUP BY deptno)

Single-row operator with

Single-row operator with

multiple-row subquery

multiple-row subquery

Will This Statement Work?Will This Statement Work?Will This Statement Work?Will This Statement Work?

no rows selectedno rows selected

Subquery returns no values

Subquery returns no values

SELECT ename, job FROM emp WHERE job = (SELECT job FROM emp WHERE ename='SMYTHE')

Multiple-Row SubqueriesMultiple-Row SubqueriesMultiple-Row SubqueriesMultiple-Row Subqueries– Return more than one row– Use multiple-row comparison operators

– Return more than one row– Use multiple-row comparison operators

Operator

IN

ANY

ALL

Meaning

Equal to any member in the list

Compare value to each value returned by

the subquery

Compare value to every value returned by

the subquery

Using ANY Operator Using ANY Operator in Multiple-Row Subqueriesin Multiple-Row Subqueries

Using ANY Operator Using ANY Operator in Multiple-Row Subqueriesin Multiple-Row Subqueries

9508001100

1300

EMPNO ENAME JOB--------- ---------- --------- 7654 MARTIN SALESMAN 7521 WARD SALESMAN

EMPNO ENAME JOB--------- ---------- --------- 7654 MARTIN SALESMAN 7521 WARD SALESMAN

SELECT empno, ename, job FROM emp WHERE sal < ANY (SELECT sal FROM emp WHERE job = 'CLERK') AND job <> 'CLERK'

Using ALL Operator Using ALL Operator in Multiple-Row Subqueriesin Multiple-Row Subqueries

Using ALL Operator Using ALL Operator in Multiple-Row Subqueriesin Multiple-Row Subqueries

2916.6667

2175

1566.6667

EMPNO ENAME JOB--------- ---------- --------- 7839 KING PRESIDENT 7566 JONES MANAGER 7902 FORD ANALYST 7788 SCOTT ANALYST

EMPNO ENAME JOB--------- ---------- --------- 7839 KING PRESIDENT 7566 JONES MANAGER 7902 FORD ANALYST 7788 SCOTT ANALYST

SELECT empno, ename, job FROM emp WHERE sal > ALL (SELECT avg(sal) FROM emp GROUP BY deptno)

SubquerySubquerySubquerySubquery

SELECT ordid, prodid, qty FROM item WHERE prodid IN (SELECT prodid FROM item WHERE ordid = 605) AND qty IN (SELECT qty FROM item WHERE ordid = 605) AND ordid <> 605

Display the order number, product number, and quantity of any item in which the product number and quantity match any product number and any quantity of an item in order 605.

Display the order number, product number, and quantity of any item in which the product number and quantity match any product number and any quantity of an item in order 605.

SubquerySubquerySubquerySubquery

SELECT ename, deptno, sal, comm FROM emp WHERE sal IN (SELECT sal FROM emp WHERE deptno = 30) AND

ISNULL(comm,-1) IN (SELECT ISNULL(comm,-1) FROM emp WHERE deptno = 30)

Display the name, department number, salary, and commission of any employee whose salary and commission matches the commission and salary of any employee in department 30.

Display the name, department number, salary, and commission of any employee whose salary and commission matches the commission and salary of any employee in department 30.

Null Values in a SubqueryNull Values in a SubqueryNull Values in a SubqueryNull Values in a Subquery

SELECT employee.ename FROM emp employee WHERE employee.empno NOT IN (SELECT manager.mgr FROM emp manager)no rows selected.no rows selected.

SELECT employee.ename FROM emp employee WHERE employee.empno NOT IN (SELECT ISNULL(manager.mgr,0) FROM emp manager)

Using a Subquery Using a Subquery in the FROM Clausein the FROM ClauseUsing a Subquery Using a Subquery

in the FROM Clausein the FROM Clause

ENAME SAL DEPTNO SALAVG---------- --------- --------- ----------KING 5000 10 2916.6667JONES 2975 20 2175SCOTT 3000 20 2175...6 rows selected.

ENAME SAL DEPTNO SALAVG---------- --------- --------- ----------KING 5000 10 2916.6667JONES 2975 20 2175SCOTT 3000 20 2175...6 rows selected.

SELECT a.ename, a.sal, a.deptno, b.salavg FROM emp a, (SELECT deptno, avg(sal) salavg FROM emp GROUP BY deptno) b WHERE a.deptno = b.deptno AND a.sal > b.salavg

Some Data TypesSome Data Types

IntegersIntegers

bigintInteger (whole number) data from -2^63 (-9223372036854775808) through 2^63-1

(9223372036854775807).int

Integer (whole number) data from -2^31 (-2,147,483,648) through 2^31 - 1 (2,147,483,647).

smallintInteger data from 2^15 (-32,768) through 2^15 - 1

(32,767).tinyint

Integer data from 0 through 255.

bitbit

Integer data with either a 1 or 0 value.

decimal and numericdecimal and numericdecimal

Fixed precision and scale numeric data from -10^38 +1 through 10^38 –1.

numeric

Functionally equivalent to decimal.

money and smallmoney money and smallmoney money

Monetary data values from -2^63 (-922,337,203,685,477.5808) through 2^63 -

1 (+922,337,203,685,477.5807), with accuracy to a ten-thousandth of a

monetary unit.smallmoney

Monetary data values from -214,748.3648 through +214,748.3647, with accuracy to a

ten-thousandth of a monetary unit.

datetime and smalldatetime datetime and smalldatetime

datetimeDate and time data from January 1,

1753, through December 31, 9999, with an accuracy of three-hundredths of a

second, or 3.33 milliseconds.smalldatetime

Date and time data from January 1, 1900, through June 6, 2079, with an

accuracy of one minute.

Character StringsCharacter Strings

charFixed-length non-Unicode character data with a

maximum length of 8,000 characters.

varcharVariable-length non-Unicode data with a maximum of

8,000 characters.

textVariable-length non-Unicode data with a maximum

length of 2^31 - 1 (2,147,483,647) characters.

Single-Row Functions

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