Equivalent of Microsoft SQL Server IDENTITY column in MySQL is AUTO_INCREMENT. The IDENTITY in SQL Server acts like AUTO_INCREMENT in MySQL.
The syntax is as follows −
CREATE TABLE yourTableName ( yourColumnName1 dataType NOT NULL AUTO_INCREMENT, yourColumnName2 dataType, . . . N, PRIMARY KEY(yourColumnName1) );
In MySQL, you need to use primary key if your column is auto_increment otherwise MySQL will give an error. Look at the error −
mysql> create table EquivalentOfIdentityInMySQL -> ( -> ProductId int NOT NULL AUTO_INCREMENT, -> ProductName varchar(30) -> ); ERROR 1075 (42000) − Incorrect table definition; there can be only one auto column and it must be defined as a key
To remove the above error, you need to make ProductId as primary key. The declaration of MySQL AUTO_INCREMENT is as follows with ProductId set as primary key −
mysql> create table EquivalentOfIdentityInMySQL -> ( -> ProductId int NOT NULL AUTO_INCREMENT, -> ProductName varchar(30) -> , -> PRIMARY KEY(ProductId) -> ); Query OK, 0 rows affected (0.59 sec)
If you won’t pass any value for the column ProductId, MySQL begins auto_increment from 1 and the next number increments by 1 by default.
To check the ProductId column, let us insert some records in the table using insert command. The query is as follows −
mysql> insert into EquivalentOfIdentityInMySQL(ProductName) values('Product-1');
Query OK, 1 row affected (0.14 sec)
mysql> insert into EquivalentOfIdentityInMySQL(ProductName) values('Product-2');
Query OK, 1 row affected (0.14 sec)
mysql> insert into EquivalentOfIdentityInMySQL(ProductName) values('Product-34');
Query OK, 1 row affected (0.10 sec)Display all records from the table using select statement. The query is as follows −
mysql> select *from EquivalentOfIdentityInMySQL;
The following is the output −
+-----------+-------------+ | ProductId | ProductName | +-----------+-------------+ | 1 | Product-1 | | 2 | Product-2 | | 3 | Product-34 | +-----------+-------------+ 3 rows in set (0.00 sec)
Look at the column ProductId, we did not pass any value for this column but we are getting the number beginning from 1 and next number increments by 1.