•id int primary key
•constraint pk_temp_id primary key(id)
•alter删除主键约束 ：alter table temp drop primary key;
•alter添加主键 ：alter table temp add primary key(name, pwd);
•alter修改列为主键 ：alter table temp modify id int primary key;
•
• 设置主键自增：auto_increment
•id int auto_increment primary key,
转载于:https://my.oschina.net/u/3368968/blog/865325