mysql之查找所有数据库中没有主键的表问题

select table_schema,table_name from information_schema.tables 
where (table_schema,table_name) not in(
    select distinct table_schema,table_name from information_schema.columns where COLUMN_KEY='PRI'    
)
and table_schema not in (
    'sys','mysql','information_schema','performance_schema' --排除系统库
);

create table users
(
  name   varchar(50)             null,
  salt   char(4)               null comment '盐',
  password varchar(255)            null comment '密码',
  create_at timestamp default CURRENT_TIMESTAMP null comment '创建时间',
  update_at timestamp default CURRENT_TIMESTAMP not null on update CURRENT_TIMESTAMP comment '修改时间',
  tid    int unsigned auto_increment
    primary key
)
  charset = utf8;

alter table users modify tid int not null;

alter table users drop primary key;

alter table users change tid id int unsigned auto_increment primary key;