server子查询连接错误

Question

我希望更新GroupID列的massemail_emailmaster，并将其设置为存储在massemail_groupmaster上的值。这两个表都有GroupName列，这是我用来加入子查询的。但是下面的查询会给我带来错误。错误消息是a3附近不正确的语法。我不明白这里的语法错误。请帮帮忙。

UPDATE [dbo].[massmail_emailmaster]  a3
set a3.GroupId =
      (select TOP 1 a1.GroupID from [dbo].[massmail_groupmaster] a1 
         join [dbo].[massmail_emailmaster] a2
      on a1.[groupname] = a2.[groupname]
where a3.[GroupName]=a2.[GroupName]) 

表[dbo]. [massmail_emailmaster]的DDL

(ClientID, varchar(50)),
           (uid, int)
           (Name, varchar(100))
           (GroupName, varchar(100))
           (Email, varchar(100))
           GroupId, int)

表的DDL

[dbo]. [massmail_groupmaster]
 (Clientid, varchar(50))
           ,(uid, int)
           ,(groupname, varchar(100))
(GroupId,int))

Answer 1

以后在update子句中定义别名时，可以在from中使用它。(这是一种“不正常”的情况，别名是在第一次使用之后定义的。)

UPDATE a3
    set GroupId = (select TOP 1 a1.GroupID
                   from [dbo].[massmail_groupmaster] a1
                   where a1.[groupname] = a3.[groupname]
                  )
    FROM [dbo].[massmail_emailmaster] a3;

Answer 2

UPDATE  a2
SET a2.GroupId = (SELECT TOP 1 a.GroupID 
                   FROM [dbo].[massmail_groupmaster] a 
                   INNER JOIN [dbo].[massmail_emailmaster] b
                   ON a.[groupname] = b.[groupname]
                  ) 
FROM  [dbo].[massmail_emailmaster] a2
WHERE a.[groupname] = a2.[groupname]