[MySQL]mysql update select 从查询结果中更新数据

参考自:https://blog.youkuaiyun.com/qq_39840681/article/details/79401795

https://blog.youkuaiyun.com/qq_36823916/article/details/79403696

 

# 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 

 

update A inner join(select id,name from B) c on A.id = c.id set A.name = c.name;