ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be def

        如下：

mysql> create table tbx(
    -> id int unsigned not null  auto_increment,
    -> score int not null
    -> );
ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
mysql> 

       什么意思呢？ 自增列只能有1列， 且这列必须为key,  如下便OK:

mysql> create table tbx(
    -> id int unsigned not null  auto_increment primary key,
    -> score int not null
    -> );
Query OK, 0 rows affected (0.01 sec)
 
mysql> 

      good