MYSQL MYSQL DEFINITION DEFINITION MySQL, pronounced either "My S-Q- L" or "My Sequel," is an open source relational database management system. It is based on the structure query language (SQL), which is used for adding, removing, and modifying information in the database. Standard SQL commands, such as ADD, DROP, INSERT, and UPDATE can be used with MySQL.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
MYSQLMYSQLDEFINITIONDEFINITION MySQL, pronounced either "My S-Q-L" or "My
Sequel," is an open source relational database management system. It is based on the structure query language (SQL), which is used for adding, removing, and modifying information in the database. Standard SQL commands, such as ADD, DROP, INSERT, and UPDATE can be used with MySQL.
Explanation:Explanation: REPLACE works exactly like INSERT, except
that if an old record in the table has the same value as a new record on a unique index, the old record is deleted before the new record is inserted.
UPDATEUPDATESyntax:Syntax: UPDATE [table] SET [column]=[value] WHERE [criteria]
UPDATE Used_Vehicles SET mileage=66000 WHERE vehicle_id=1; UPDATE [table] SET [column]=[value] WHERE [criteria]
Example: UPDATE Used_Vehicles SET mileage=66000 WHERE vehicle_id=1;
Explanation: UPDATE updates columns in existing table rows with new values.
The SET clause indicates which columns to modify and the values they should be given. The WHERE clause, if given, specifies which rows should be updated. Otherwise all rows are updated.
ADVANCED COMMANDSADVANCED COMMANDS
AS ALTER and ADD UNION JOIN TEMPORARY Table TRUNCATE Table
ASASSyntax: SELECT <columns>FROM
<existing_table_name>AS <new_table_name>
Example: SELECT t1.name -> FROM artists -> AS t1;
Explanation: It is used to create a shorthand reference to elements with long names to make the SQL statements shorter and reduce the chance of typos in the longer names.
ALTERING THE DATABASE ALTERING THE DATABASE STRUCTURE AND ADDING DATASTRUCTURE AND ADDING DATA
Syntax:ALATER TABLE tablenameADD clm_name type
Example:Example: ALTER TABLE cds -> ADD producerID INT(3);
UNION JOINSUNION JOINSSyntax: Select <fields>from <table> where <condition> unionSELECT <fields> FROM <table>WHERE <condition>
Example: SELECT artist FROM artists WHERE (artists.name LIKE 'P
%') UNION SELECT artists.name FROM artists WHERE
(artists.name LIKE 'G%');
Explanation: Union Joins allow the results of two queries to be
combined into one outputted result set. This is done by having the 2 (or more) queries glued together by the UNION operator.
CREATING THE TEMPORARY TABLECREATING THE TEMPORARY TABLE
Definition: The syntax for creating temporary tables is almost identical that
used for creating a normal table. Except that there is an extra TEMPORARY clause.
Use: Mysql COUNT function is useful in counting the
number of records.
MAX AND MIN FUNCTIONSMAX AND MIN FUNCTIONSSyntax:
SELECT MAX(Col_name) FROM table_name;
Use:
MySQL MAX function is used to find out the record with maximum value among a record set.
MIN( )MIN( )
Syntax:
SELECT MIN(Col_name) FROM table_name;
Use:
MySQL MIN function is used to find out the record with minimum value among a record set.
AVG( )
Syntax: SELECT AVG(Col_name) FROM table_name;
Use: MySQL AVG function is used to find out the
average of a field in various records.
SUM( )SUM( )Syntax:
SELECT SUM(Col_name) FROM table_name;
Use:
MySQL SUM function is used to find out the sum of a field in various records.
RAND( )RAND( )
Syntax:
SELECT RAND( );
Use:
MySQL has a RAND function that can be invoked to produce random numbers between 0 and 1
NUMERIC FUNCTIONSNUMERIC FUNCTIONS
Syntax:
ABS(X);Use:
The ABS() function returns the absolute value
of X.
BIT_COUNT( )BIT_COUNT( )
Synatx:Synatx:
BIT_COUNT(numeric_value)Use: Use:
The BIT_COUNT() function returns the
number of bits that are active in numeric_value.
CEIL( ) / CEILING( )CEIL( ) / CEILING( )
Syntax: CEIL(X)
CEILING(X)Use: These function return the smallest integer value
that is not smaller than X.
FLOOR( )FLOOR( )
Syntax:
FLOOR(X)
Use:
This function returns the largest integer value that is not greater than X.
GREATEST( )GREATEST( )
Syntax:
GREATEST(n1,n2,n3,..........)
Use:
The GREATEST() function returns the greatest value in the set of input parameters (n1, n2, n3,
a nd so on).
LEAST( )LEAST( )
Syntax:
LEAST(N1,N2,N3,N4,......)
Use: Its purpose is to return the least-valued item
from the value list (N1, N2, N3, and so on).
PI( )PI( )
Syntax:
PI()Use:
This function simply returns the value of pi.
MySQL internally stores the full double-precision value of pi.
POW( ) / POWER( )POW( ) / POWER( )
Syntax:
POW(X,Y)POWER(X,Y)
Use:
These two functions return the value of X raised to the power of Y.
ROUND( )ROUND( )
Syntax :
ROUND(X)ROUND(X,D)
Use:
This function returns X rounded to the nearest integer. If a second argument, D, is supplied,
then the function returns X rounded to D decimal places.
SIN( )SIN( )
Syntax:
SIN(X)Use:
This function returns the sine of X
SQRT( )
Syntax:
SQRT(X)Use:
This function returns the non-negative square
root of X.
TRUNCATE( )TRUNCATE( )
Syntax:
TRUNCATE(X,D)Use:
This function is used to return the value of X
truncated to D number of decimal places.
STRING FUNTIONSSTRING FUNTIONS
Syntax:
ASCII(str)Use:
Returns the numeric value of the leftmost
character of the string str.
BIN( )
Syntax:
BIN(N)Use:
Returns a string representation of the binary
value of N,
BIT LENGTH( )Syntax:
BIT_LENGTH(str)
Use:
Returns the length of the string str in bits. Example:
SELECT BIT_LENGTH('text');BIT_LENGTH('text')
32
CHAR( )Syntax:
CHAR(N,... [USING charset_name])
Use: CHAR() interprets each argument N as an
integer and returns a string consisting Example:
SELECT CHAR(77,121,83,81,'76');
MySQL
CHAR LENGTHCHAR LENGTH
Syntax:
CHAR_LENGTH(str)Use:
Returns the length of the string str, measured in
characters. A multi-byte character counts as a single character
CONCAT( )CONCAT( )
Syntax:
CONCAT(str1,str2,...)Use:
MySQL CONCAT function is used to concatenate
two strings to form a single string.
FIELD( )Syntax:
FIELD(str,str1,str2,str3,...)Use:
Returns the index (position starting with 1) of str in the str1, str2, str3, ... list. Returns 0 if str is
not found.
FIND_IN_SET( )FIND_IN_SET( )
Syntax:
FIND_IN_SET(str,strlist)Use:
Returns a value in the range of 1 to N if the string
str is in the string list strlist consisting of N substrings.
INSERT( )INSERT( )
Syntax:
INSERT(str,pos,len,newstr)Use:
Returns the string str, with the substring beginning at position pos and len characters
long replaced by the string newstr.
LCASE( ) / LOWER( )LCASE( ) / LOWER( )
Syntax:
LOWER(str)Use:
Returns the string str with all characters changed
to lowercase according to the current character set mapping.
To export a database, use the mysqldump utility normally located in your mysql/bin directory . For example, to export all the tables and data for a database named guestdb.
Syntax:Syntax:mysqldump guestdb > guestdb.txt
Exporting a DatabaseExporting a Database
This will create a text file containing all the commands necessary to recreate all the tables and data found in guestdb. However, what if I want to export only one table? To do this the command is modified as follows assuming guestTbl is the table to be exported.
Syntax:mysqldump guestdb guestTbl > guestdb.txt
With the data in a text file, its time to import the data back into MySQL. This can be done by passing the commands contained in the text file into the MySQL client.
For example:mysql -p --user=username < guestdb.txt
This passes all the commands in the file into the mysql client just like you were typing them in.