sql批量更新update嵌套select更新

概述

有两张表【user】和【city】，user表的 city_uuid、city_no 和 city 表的 city_uuid、city_no 一一对应，但是 user 表只有 city_uuid，这时候需要将 city 对应的 city_no 批量更新到 user 表中

批量更新方式

第一种方式（inner join 内连接）

update u
set u.city_no = c.city_no
from user u 
inner join city c 
on u.city_uuid = c.city_uuid
where u.city_uuid is not null and u.city_no is null

第二种方式（子查询）

update u
set u.city_no = (select c.city_no from city c where u.city_uuid = c.city_uuid)
from user u

第三种方式：（笛卡尔积）

update u
set u.city_no = c.city_no  
from [user] u, city c 
where u.city_uuid = c.city_uuid

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update 多表更新

update table1 t1,table2 t2, table3 t3, ... , tablen tn
set t1.column= ?, t2.column, t3.column = ?, ... , tn.column = ?
where t1.xx= ?, t2.xx = ?, ... , tn.xx = ?

案例：（conditionUuid是user表的外键，每个conditionUuid对应两条user记录，将producter记录覆盖consumer记录的指定字段值)

update r2
set r2.userUuid = r1.userUuid, r2.userName = r1.userName , r2.age = r1.age, r2.updatedTime = '2021-02-22 22:22:22.222'
from user r1
inner join user r2
on r1.conditionUuid = r2.conditionUuid
where r1.conditionValue = 'condition-consumer-00000000000000000' and r1.userName is not null
and r2.conditionValue = 'condition-producter-0000000000000000' and r2.userName is not null