如何在更新时连接表

Question

我有以下查询:

select      count(L.ID)
from        LA inner join L on (LA.leadid = L.ID)
where       L.status = 5
and         L.city = "cityname"
and         Date(LA.Datetime) < Date_Sub(Now(), INTERVAL 6 MONTH);

查找特定城市中状态为5且年龄超过6个月(日期存储在洛杉矶)的记录.这将返回大约4k的结果.我想在每个记录上将状态值更新为1,因此我的更新如下所示:

update      L, LA
set         L.status = 1
where       L.status = 5 
and         L.city = "cityname" 
and         Date(LA.SomeDatetime) < Date_Sub(Now(), INTERVAL 6 MONTH);

但它会停止并锁定数据库.我怀疑有一个问题,因为没有加入,但我尝试类似的东西:

update      L, LA
from        L inner join LA on (L.OID = LA.leadid)
set         L.status = 1
where       L.status = 5 
and         L.syscity = "cityname" 
and         Date(LA.SomeDatetime) < Date_Sub(Now(), INTERVAL 6 MONTH);

它显然不起作用,因为更新中没有'from'.

编辑>我正在使用MySQL

Answer 1

update      L
set         L.status = 1
where       L.status = 5 
and         L.city = "cityname" 
and         EXISTS (
  select * from LA 
  where Date(LA.SomeDatetime) < Date_Sub(Now(), INTERVAL 6 MONTH)
  and LA.leadid = L.ID
)