sql - sql server 子查询连接错误

Question

我想更新 massemail_emailmaster 的 GroupID 列并将其设置为存储在 massemail_groupmaster 上的值。这两个表都有我用来加入子查询的 GroupName 列。但是以下查询给了我错误。错误消息是 a3 附近的语法不正确。我不明白这里的语法错误。请帮忙。

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]) 

表的 DDL[dbo]. [massmail_emailmaster]

(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

您可以在update稍后在from子句中定义别​​名时使用别名。（这是一种“反常”情况，别名是在第一次使用后定义的。）

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]