连表更新

实践：

1、

商品表记录了品牌名，现在需要找回品牌Id

通过品牌名，关联查询更新

UPDATE Goods g LEFT JOIN GoodsBrand b

ON g.brand_name=b.Name

SET g.BrandId=IFNULL(b.Id,0) WHERE 1;

 

 

update visit_copy c left join( SELECT SUM(pv) AS sumpv,uid FROM visit_middle GROUP BY uid ) d on c.uid = d.uid set c.total = d.sumpv;

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