MySQL Set primary key auto Grow

Create a database and create a table.

SQL code

2. mysql> Create database ssh2;
4. Query OK, 1 row affected (0.04 sec)
6.   
8. mysql> use SSH2;
10. Database changed
12. mysql> Create table user(
14. -id integer primary key,
16. - firstname varchar(+) not null,
18. - lastname varchar(+) not null,
20. -Age integer
22. );
24. Query OK, 0 rows Affected (0.46 sec)

Add a self-increment function to the primary key:
Java code

1. mysql> ALTER TABLE user modify ID integer auto_increment;
2. Query OK, 1 row affected (0.28 sec)
3. Records: 1 Duplicates: 0 Warnings: 0

In this way, the ID of the primary key in the user table above can be self-increment.









add default values and auto-increment to the primary key ID above.
Java code

2. mysql> ALTER TABLE user modify ID integer auto_increment;
4. Query OK, 0 rows affected (0.39 sec)
6. Records: 0 Duplicates: 0 Warnings: 0
8.   
10. mysql> ALTER TABLE user Modify ID integer default ' 1 ';
12. Query OK, 0 rows affected (0.16 sec)
14. Records: 0 Duplicates: 0 Warnings: 0
16.   
18. mysql> ALTER TABLE user modify ID integer auto_increment;
20. Query OK, 1 row affected (0.28 sec)
22. Records: 1 Duplicates: 0 Warnings: 0

MySQL Get system time:
Java code

1. mysql> ALTER TABLE user add createtime timestamp default current_timestamp;
2. Query OK, 2 rows affected (0.17 sec)
3. Records: 2 Duplicates: 0 Warnings: 0

MySQL Settings primary key cannot be empty and will grow automatically (there is no default value set here, but the default is 1, starting from 1 growth.) ) and get the system default date:

If you want to create a table of the same data structure from a table:

CREATE TABLE Newtbname SELECT * from tab where 0;

This new table has the same data structure as the original table but does not set the primary key auto-growth

ALTER TABLE Modify ID integer primary key auto_increment

This ensures that the primary key ID is automatically increased in the database

MySQL Set primary key auto Grow