MySQL5.5报错ERROR 1075 42000 Incorrect table definition

2022-08-03 16:44:42

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--给表增加自增字段的时候报错

mysql> desc t7;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| name | varchar(20) | YES |     | NULL    |       |
| id    | int(4)      | YES |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> alter table t7 add id2 int(4) auto_increment;
ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key

报错原因：自增字段没有被定义为一个key。

解决办法：可以将新增字段定义为unique key或primary key。

mysql> alter table t7 add id2 int(4) auto_increment primary key;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table t7 drop column id2;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table t7 add id2 int(4) auto_increment unique key;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0

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