一：关联不同的表更新

1: 通过where关联更新

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

2：子查询更新

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

子查询更新优化：

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`);

转为：

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;