T1表 结构
id name school
1 ming1 清华大学
2 ming2 北京大学
3 ming3 复旦大学
T2表 结构
id student school
11 ming1 牛津大学
12 ming3 剑桥大学
T1表的name 和 T2表的 student 值是 1对1 的对应。
需求：这两个字段的值相同时，根据B表的school更新A表的school。
语句：
update t1 set school = (select school from t2 where name=student) where exists (select * from t2 as b where name = b.student);
结果：
T1表 结构
id name school
1 ming1 牛津大学
2 ming2 北京大学
3 ming3 剑桥大学
注意：
条件里不要再加本身要更新的表,
PS:
关联查询语句：
select aii.update_time,pn.public_time,pn.* from t_apply_item_instance aii, t_public_notice pn where pn.apply_item_instance_uuid = aii.uuid and
aii.apply_item_uuid in ('0101','0102','0103','0104','0105','0106','0201','0202','0203','0204','0205','0206') and aii.apply_status = 21
and pn.public_type = 1
更新语句：
update t_public_notice set public_time =
(select aii.update_time from t_apply_item_instance aii where apply_item_instance_uuid = aii.uuid and
aii.apply_item_uuid in ('0101','0102','0103','0104','0105','0106','0201','0202','0203','0204','0205','0206') and aii.apply_status = 21
and public_type = 1 )
where exists
(select t1.* from t_apply_item_instance as t1 where apply_item_instance_uuid = t1.uuid and
t1.apply_item_uuid in ('0101','0102','0103','0104','0105','0106','0201','0202','0203','0204','0205','0206') and t1.apply_status = 21
and public_type = 1)
update的表在后面的条件里面是没有了的