自增列允许插入0值

mysql> set sql_mode="NO_AUTO_VALUE_ON_ZERO";

mysql> insert into d select 0;
Query OK, 1 row affected (0.19 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> select * from d;
+---+
| a |
+---+
| 0 |
+---+
1 row in set (0.19 sec)

mysql> insert into d select null;
Query OK, 1 row affected (0.18 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> select * from d;
+---+
| a |
+---+
| 0 |
| 1 |
+---+