MySQL Setup self-increment field

1, MySQL each table can only have 1 self-increment field, this self-increment field can be used as the primary key, also can use as a non-primary key, but note that the self-increment field as a non-primary key to use must be added a unique index, or the system will be error

1 set the auto-grow field as the primary key    CREATE TABLE T1 (    ID INT auto_increment PRIMARY KEY,    sid int    ); 2 ) To set the Autogrow field to a non-primary key    CREATE TABLE T2 (    sid int PRIMARY KEY,    ID INT auto_increment UNIQUE    ); 3 set the autogrow field to a non-primary key if adding a unique index will give an error    CREATE TABLE t3 (    sid int PRIMARY KEY,    ID INT auto_increment    );

2. Self-increment field in MySQL when you delete data and reinsert the data, the self-increment field does not start counting again.

MySQL Setup self-increment field