Does using SERIAL as column name already includes 'NOT NULL' in MySQL?

In MySQL, SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE. So, do not use NOT NULL after SERIAL, since it already includes NOT NULL as part of its definition.

Let us see an example and create a table. Here, we have a column with the name “serial” −

mysql> create table DemoTable (    Id serial ); Query OK, 0 rows affected (0.42 sec)

Insert some records in the table using insert command. We aren’t including any value while inserting −

mysql> insert into DemoTable values(); Query OK, 1 row affected (0.24 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.07 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+----+ | Id | +----+ | 1 | | 2 | | 3 | | 4 | | 5 | | 6 | +----+ 6 rows in set (0.00 sec)