---
title: MySql
category: Databases
---
### Create / Delete Database
    CREATE DATABASE dbNameYouWant
    CREATE DATABASE dbNameYouWant CHARACTER SET utf8
    DROP DATABASE dbNameYouWant
    ALTER DATABASE dbNameYouWant CHARACTER SET utf8
    
### Backup Database to SQL File
    mysqldump -u Username -p dbNameYouWant > databasename_backup.sql
    
### Restore from backup SQL File
    mysql - u Username -p dbNameYouWant < databasename_backup.sql
    
### Repair Tables After Unclean Shutdown
    mysqlcheck --all-databases
    mysqlcheck --all-databases --fast
### 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 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 ...
    
### Select - 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
    
### 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
    
### Create / 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 (...)
      
    *Drop*
    DROP TABLE table
    DROP TABLE IF EXISTS table
    DROP TABLE table1, table2, ...
      
    *Alter*
    ALTER TABLE table MODIFY 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
    
### Keys  
    CREATE TABLE table (..., PRIMARY KEY (field1, field2))
    CREATE TABLE table (..., FOREIGN KEY (field1, field2) REFERENCES table2
    (t2_field1, t2_field2))
    
    
### Users and Privileges
    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'@'host'; -- one permission only
    REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'user'@'host'; -- all permissions
      
    SET PASSWORD = PASSWORD('new_pass')
    SET PASSWORD FOR 'user'@'host' = PASSWORD('new_pass')
    SET PASSWORD = OLD_PASSWORD('new_pass')
      
    DROP USER 'user'@'host'
    host ‘%’ indicates any host.
    
    
### 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) LONG (max=4Go)
     Ex: VARCHAR(32), TINYTEXT, LONGBLOB, MEDIUMTEXT
     
     ENUM ('value1', 'value2', ...) -- (default NULL, or '' if NOT NULL)
    
### Reset Root Password
    $ /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</code>