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;