MySql通过查询结果集更新数据的方法介绍

select user_id from user_info where user_name = '' ;

select * from user_card where user_id in (上面的结果集) ;

通过代码更新数据

SELECT

  c.user_id ,

  c.user_name

FROM

    user_info AS u

LEFT JOIN user_card AS c ON u.user_id = c.user_id

WHERE

    u.user_name = ''; 

通过代码更新数据

先写出更新语句

UPDATE `user_info` as u SET u.user_name = '结果集' ;

再获取条件结果集

SELECT

  c.user_id ,

  c.user_name

FROM

    user_info AS u

LEFT JOIN user_card AS c ON u.user_id = c.user_id

WHERE

    u.user_name = ''; 

最后内联更新

UPDATE `user_info` as u

INNER JOIN

(

    SELECT

      c.user_id ,

      c.user_name

    FROM

        user_info AS u

    LEFT JOIN user_card AS c ON u.user_id = c.user_id

    WHERE

        u.user_name = ''; 

) as r ON u.user_id = r.user_id SET u.user_name = r.user_name ;