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;