MySQL CheatSheet - Subham Karmakar

mysql -u root -p

Exit / Clear Screen

Exit

exit;

Clear Screen

system clear

Create / Show / Use / Delete / Modify Database

Create

CREATE DATABASE DatabaseName;
CREATE DATABASE DatabaseName CHARACTER SET utf8;

Show

SHOW DATABASES;

Use

USE DatabaseName;

Delete

DROP DATABASE DatabaseName;

Modify

ALTER DATABASE DatabaseName CHARACTER SET utf8;

Main Data Types

TINYINT (1o: -217+128)
SMALLINT (2o: +-65 000)
MEDIUMINT (3o: +-16 000 000)
INT (4o: +- 2 000 000 000)
BIGINT (8o: +-9.10^18)

Precise interval: -(2^(8*N-1)) -> (2^8*N)-1

*** INT(2) = "2 digits displayed" -- NOT "number with 2 digits max" !

FLOAT(M,D)
DOUBLE(M,D)
FLOAT(D=0->53)

*** 8,3 -> 12345.678 -- NOT 12345678.123 !

TIME (HH:MM)
YEAR (AAAA)
DATE (AAAA-MM-JJ)
DATETIME (AAAA-MM-JJ HH:MM; années 1000->9999)
TIMESTAMP (like DATETIME, but 1970->2038, compatible with Unix)

VARCHAR (single-line; explicit size)
TEXT (multi-lines; max size=65535)
BLOB (binary; max size=65535)

Variants for TEXT&BLOB:
`TINY` (max=255), `MEDIUM` (max=~16000), and `LONG` (max=4Go). Ex: `VARCHAR(32)`, `TINYTEXT`, `LONGBLOB`, `MEDIUMTEXT`

ENUM ('value1', 'value2', ...) -- (default NULL, or '' if NOT NULL)

Create / Show / Delete / Modify Table

Create

CREATE TABLE table (field1 type1, field2 type2);
CREATE TABLE table (field1 type1, field2 type2, INDEX (field));
CREATE TABLE table (field1 type1, field2 type2, PRIMARY KEY (field1));
CREATE TABLE table (field1 type1, field2 type2, PRIMARY KEY (field1,field2));

CREATE TABLE table1 (fk_field1 type1, field2 type2, ...,
  FOREIGN KEY (fk_field1) REFERENCES table2 (t2_fieldA))
	[ON UPDATE|ON DELETE] [CASCADE|SET NULL]

CREATE TABLE table1 (fk_field1 type1, fk_field2 type2, ...,
  FOREIGN KEY (fk_field1, fk_field2) REFERENCES table2 (t2_fieldA, t2_fieldB))

CREATE TABLE table IF NOT EXISTS;

CREATE TEMPORARY TABLE table;

Show

SHOW TABLES;

Drop

DROP TABLE table;
DROP TABLE IF EXISTS table;
DROP TABLE table1, table2, ...

Alter

ALTER TABLE table MODIFY field1 type1
ALTER TABLE table MODIFY COLUMN field1 type1
ALTER TABLE table MODIFY field1 type1 NOT NULL ...
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1 NOT NULL ...
ALTER TABLE table ALTER field1 SET DEFAULT ...
ALTER TABLE table ALTER field1 DROP DEFAULT
ALTER TABLE table ADD new_name_field1 type1
ALTER TABLE table ADD new_name_field1 type1 FIRST
ALTER TABLE table ADD new_name_field1 type1 AFTER another_field
ALTER TABLE table DROP field1
ALTER TABLE table ADD INDEX (field);

Change field order

ALTER TABLE table MODIFY field1 type1 FIRST
ALTER TABLE table MODIFY field1 type1 AFTER another_field
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1 FIRST
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1 AFTER another_field

Browsing

SHOW DATABASES;
SHOW TABLES;
SHOW FIELDS FROM table / DESCRIBE table;
SHOW CREATE TABLE table;
SHOW PROCESSLIST;
KILL process_number;

Select

SELECT * FROM table;
SELECT * FROM users WHERE age BETWEEN 20 AND 25;
SELECT * FROM users WHERE dept LIKE '%e%';
SELECT * FROM users WHERE dept NOT LIKE 'd%';
SELECT * FROM users WHERE dept IN ('design', 'sales');
SELECT * FROM users ORDER BY last_name ASC;
SELECT * FROM users ORDER BY last_name DESC;
SELECT CONCAT(first_name, ' ', last_name) AS 'Name', dept FROM users;
SELECT * FROM table1, table2;
SELECT field1, field2 FROM table1, table2;
SELECT ... FROM ... WHERE condition
SELECT ... FROM ... WHERE condition GROUPBY field;
SELECT ... FROM ... WHERE condition GROUPBY field HAVING condition2;
SELECT ... FROM ... WHERE condition ORDER BY field1, field2;
SELECT ... FROM ... WHERE condition ORDER BY field1, field2 DESC;
SELECT ... FROM ... WHERE condition LIMIT 10;
SELECT DISTINCT field1 FROM ...
SELECT DISTINCT field1, field2 FROM ...

Join

SELECT ... FROM t1 JOIN t2 ON t1.id1 = t2.id2 WHERE condition;
SELECT ... FROM t1 LEFT JOIN t2 ON t1.id1 = t2.id2 WHERE condition;
SELECT ... FROM t1 JOIN (t2 JOIN t3 ON ...) ON ...

Conditions

field1 = value1
field1 <> value1
field1 LIKE 'value _ %'
field1 IS NULL
field1 IS NOT NULL
field1 IS IN (value1, value2)
field1 IS NOT IN (value1, value2)
condition1 AND condition2
condition1 OR condition2

Backup Database to SQL File (Bash Commands)

mysqldump -u Username -p dbNameYouWant > databasename_backup.sql

Restore from backup SQL File (Bash Commands)

mysql - u Username -p dbNameYouWant < databasename_backup.sql

Repair Tables After Unclean Shutdown (Bash Commands)

mysqlcheck --all-databases
mysqlcheck --all-databases --fast

Insert

INSERT INTO table1 (field1, field2) VALUES (value1, value2);

Delete

DELETE FROM table1 / TRUNCATE table1
DELETE FROM table1 WHERE condition
DELETE FROM table1, table2 FROM table1, table2 WHERE table1.id1 = table2.id2 AND condition

Update

UPDATE table1 SET field1=new_value1 WHERE condition;
UPDATE table1, table2 SET field1=new_value1, field2=new_value2, ... WHERE table1.id1 = table2.id2 AND condition;

Keys

CREATE TABLE table (..., PRIMARY KEY (field1, field2))
CREATE TABLE table (..., FOREIGN KEY (field1, field2) REFERENCES table2
(t2_field1, t2_field2))

Users and Privileges

CREATE USER 'user'@'localhost';
CREATE USER 'someuser'@'localhost' IDENTIFIED BY 'somepassword';

SELECT User FROM mysql.user;
SELECT User, Host FROM mysql.user;
SELECT * FROM mysql. user


GRANT ALL PRIVILEGES ON * . * TO 'someuser'@'localhost';
GRANT ALL PRIVILEGES ON base.* TO 'user'@'localhost' IDENTIFIED BY 'password';
GRANT SELECT, INSERT, DELETE ON base.* TO 'user'@'localhost' IDENTIFIED BY 'password';
REVOKE ALL PRIVILEGES ON base.* FROM 'user'@'localhost'; -- one permission only
REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'user'@'localhost'; -- all permissions
FLUSH PRIVILEGES;

SHOW GRANTS FOR 'someuser'@'localhost';

SET PASSWORD = PASSWORD('new_pass');
SET PASSWORD FOR 'user'@'host' = PASSWORD('new_pass');
SET PASSWORD = OLD_PASSWORD('new_pass');

DROP USER 'user'@'localhost';

Reset Root Password (Bash Commands)

$ /etc/init.d/mysql stop

$ mysqld_safe --skip-grant-tables

$ mysql (On another terminal)
mysql> UPDATE mysql.user SET password=PASSWORD('new_pass') WHERE user='root';

(Switch back to the mysqld_safe terminal and kill the process using Control)
$ /etc/init.d/mysql start