MySQL 从一张表update字段到另外一张表中

先来几个简单的示例

solution 1:  1列

update student s, city c
  set s.city_name = c.name
 where s.city_code = c.code;

solution 2:  多个列

update a, b 

set a.title=b.title, a.name=b.name
where a.id=b.id

solution 3: 子查询

update student s set city_name = (select name from city where code = s.city_code);

我们再来看几个负责写的

例如: 把表 tk_zyt_scenery_order的 字段更新到 t_advs_order中去, 一般可能会这样写:

update t_advs_order set
 
 attribute1=(select o.order_state from tk_zyt_scenery_order o where o.order_id=`on`),
 
 attribute2=(select o.order_state from tk_zyt_scenery_order o where o.order_id=`on`)
 
 where exists (select o.order_state from tk_zyt_scenery_order o where o.order_id=`on`);

这样效率比较低下, 优化写法:

update t_advs_order a inner join tk_zyt_scenery_order s on s.order_id=a.`on` set
 
 a.attribute1=s.order_id,
 
 a.attribute2=s.order_id;