![]() ![]() If the new value is lower than the current maximum value, the AUTO_INCREMENT value remains unchanged. If the new value is higher than the current maximum value, the AUTO_INCREMENT value is updated, so the next value will be higher. ![]() If the key is primary or unique, the value must not already exist in the key. It is possible to specify a value for an AUTO_INCREMENT column. See also AUTO_INCREMENT Handling in InnoDB. When the server restarted, the counter was re-initialized to the highest value used in the table, which canceled the effects of any AUTO_INCREMENT = N option in the table statements). Prior to MariaDB 10.2.3, InnoDB used an auto-increment counter that was stored in memory. ALTER TABLE animals AUTO_INCREMENT = 8 INSERT INTO animals ( name ) VALUES ( 'aardvark' ) SELECT * FROM animals + -+-+ | id | name | + -+-+ | 1 | dog | | 2 | cat | | 3 | penguin | | 4 | fox | | 5 | whale | | 6 | ostrich | | 8 | aardvark | + -+-+ SET insert_id = 12 INSERT INTO animals ( name ) VALUES ( 'gorilla' ) SELECT * FROM animals + -+-+ | id | name | + -+-+ | 1 | dog | | 2 | cat | | 3 | penguin | | 4 | fox | | 5 | whale | | 6 | ostrich | | 8 | aardvark | | 12 | gorilla | + -+-+ InnoDBĪUTO_INCREMENT is persistent in InnoDB. LAST_INSERT_ID() can be used to see the last AUTO_INCREMENT value inserted by the current session. You can use an ALTER TABLE statement to assign a new value to the auto_increment table option, or set the insert_id server system variable to change the next AUTO_INCREMENT value inserted by the current session. row *************************** Table : t Create Table : CREATE TABLE ` t ` ( ` id ` bigint ( 20 ) unsigned NOT NULL AUTO_INCREMENT, ` c ` char ( 1 ) DEFAULT NULL, UNIQUE KEY ` id ` ( ` id ` ) ) ENGINE = InnoDB DEFAULT CHARSET = latin1 Setting or Changing the Auto_Increment Value SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE. CREATE TABLE animals ( id MEDIUMINT NOT NULL AUTO_INCREMENT, name CHAR ( 30 ) NOT NULL, PRIMARY KEY ( id ) ) INSERT INTO animals ( name ) VALUES ( 'dog' ),( 'cat' ),( 'penguin' ), ( 'fox' ),( 'whale' ),( 'ostrich' ) SELECT * FROM animals + -+-+ | id | name | + -+-+ | 1 | dog | | 2 | cat | | 3 | penguin | | 4 | fox | | 5 | whale | | 6 | ostrich | + -+-+ Storage engines that permit the column to be placed elsewhere are Aria, MyISAM, MERGE, Spider, TokuDB, BLACKHOLE, FederatedX and Federated. In some storage engines (including the default InnoDB), if the key consists of multiple columns, the AUTO_INCREMENT column must be the first column. It must defined as a key (not necessarily the PRIMARY KEY or UNIQUE key). The automatically generated value can never be lower than 0.Įach table can have only one AUTO_INCREMENT column. ![]() This also applies to 0, unless the NO_AUTO_VALUE_ON_ZERO SQL_MODE is enabled.ĪUTO_INCREMENT columns start from 1 by default. When you insert a new record to the table (or upon adding an AUTO_INCREMENT attribute with the ALTER TABLE statement), and the auto_increment field is NULL or DEFAULT (in the case of an INSERT), the value will automatically be incremented. The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows. Generating Auto_Increment Values When Adding the Attribute.CHECK Constraints, DEFAULT Values and Virtual Columns.Setting or Changing the Auto_Increment Value. ![]()
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