mysql update select 从查询结果中更新数据

实际案例：

UPDATE chat_messages  as a INNER JOIN (SELECT *from chat_messages  WHERE receiver='lisi' and receiver_no=2 and ( msg_id- last_id)>0 ORDER BY id LIMIT 2) as b ON a.id=b.id
SET a.last_id=a.msg_id

一下来自网上总结：

先select出来 然后在update 一下  条件不变

UPDATE tab_game_version  as a INNER JOIN tab_game_version as b ON a.id=b.id
SET a.advert_data=0 where a.advert_data is NULL


----

# update select 语句(注意:必须使用inner join)
# 语法 update a inner join (select yy from b) c on a.id =c.id set a.xx = c.yy
#SELECT knowledge_id,COUNT(0) nums FROM pro_base_timu_knowledge GROUP BY knowledge_id;
UPDATE pro_base_knowledge
INNER JOIN (
SELECT
knowledge_id,
COUNT(0) nums
FROM
pro_base_timu_knowledge
GROUP BY
knowledge_id
) b ON pro_base_knowledge.id = b.knowledge_id
SET pro_base_knowledge.timu_num = b.nums