•id int primary keyrem
•constraint pk_temp_id primary key(id)table
•alter删除主键约束 ：alter table temp drop primary key; class
•alter添加主键 ：alter table temp add primary key(name, pwd); im
•alter修改列为主键 ：alter table temp modify id int primary key;tab
•di
• 设置主键自增：auto_incrementco
•id int auto_increment primary key, ab