2.1 update和select结合使用方式 批量更新
1️⃣ inner join内连接方式
update A inner join B on A.bid=B.id set A.bname = B.name
update t_A a
inner join (select b.id,b.name from t_B b) tmpb on tmpb.id=a.bid
set a.bname=tmpb.name
2️⃣子查询方式
update u
set u.city_no = ( select c.city_no from t_city c where c.city_uid = u.city_uid)
from t_user u
3️⃣ 笛卡尔积方式
update u
set u.city_no = c.city_no
from t_user u, t_city c
where c.city_uid = u.city_uid
4️⃣update 多表更新
___mark一下，没用过___
update table1 t1,table2 t2,......,tablen tn
set t1.column=?, t2.column=?.......,tn.column=?
where t1.xx=?,t2.xx=?,......tn.xx=?
