删除主键时,出错:[Err] 1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key
alter table table_name drop primary key; # [Err] 1075
这是因为,建表时,该主键设置的是自增属性:即AUTO_INCREMENT
而自增列只能有1列,且这列必须为key,也就是建表的时候,如果是自增列,必须用primary key标识
例如该表中的 (id) 这一列:
create table if not exists table_name( id INT UNSIGNED AUTO_INCREMENT, name_people VARCHAR(40) NOT NULL, submission_time DATETIME, PRIMARY KEY(id) )ENGINE=InnoDB DEFAULT CHARSET=utf8;
解决方法:
建表时,不要加入自增属性,之后就可以删除主键,例如:
create table if not exists table_name_2( id INT UNSIGNED, name_people VARCHAR(40) NOT NULL, submission_time DATETIME, PRIMARY KEY(id) )ENGINE=InnoDB DEFAULT CHARSET=utf8;
然后可以删除主键:
alter table table_name_2 drop primary key;
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