尝试在两个表上进行左联接，但只希望右表中的一个

Question

所以我有两个桌子。

Table 1

ID    Receiver  Some  Columns

1  43523  Ba  Baa

2  82822  Boo  Boo

Table 2

ID    Receiver  Some2  Columns2

1 - 43523  OO  JJ

2 - 43523  OO  NULL

3 - 43523  OO  YABA DABA

因此，现在我想做一个left join ，在该联接中，我仅联接表2中的匹配行之一。联接将在Receiver列上，并且每个表中的ID列都不同。

我尝试了左联接，它给了我表2中的所有内容（理解）。 我在网上查看了其他查询，但迷路了。

谁能帮我这个？

编辑

开始查询（根据OP的评论）：

SELECT Table1.[ID],
       Table1.[Receiver],
       Table2.[Some2],
       Table1.[Some],
       Table1.[Columns]
  FROM Table1
  LEFT JOIN Table2
    ON Table1.Receiver = Table2.ReceiverID
 WHERE Some = 544
   AND Columns = 'xyz' 

Answer 1

尝试使用group by以使“ Receiver列唯一：

SELECT t1.*, t2.*
FROM Table1 AS t1
LEFT JOIN Table2 AS t2 ON t1.Receiver = t2.Receiver
GROUP BY t2.Receiver

Answer 2

您可以将left join更改为普通join ，因为您一直期待匹配。

为了将匹配项限制为单行，可以使用row_number over () ，其中order by子句是没有意义的，因为您不在乎要匹配的行。

SELECT Table1.[ID],
       Table1.[Receiver],
       t2.[Some2],
       Table1.[Some],
       Table1.[Columns]
  FROM Table1
  JOIN (SELECT *,
               row_number() over (partition by ReceiverID order by ReceiverID) as rn
          FROM Table2) t2
    ON Table1.Receiver = t2.ReceiverID
   AND t2.rn = 1
 WHERE Some = 544
   AND Columns = 'xyz' 

Answer 3

因为您只对每条记录都相同的一列感兴趣，所以可以使用子查询：

select t1.*, (select max(some2) from table2 t2 where t2.receiver = t1.receiver)
from table1 t1

（但是，该列始终相同，这表示表设计不正确。）

Answer 4

select *
from
    T1 as t1 inner join
    (select Receiver, min(Some2) as Some2 from T2 group by Receiver) as t2
        on t2.Receiver = t1.Receiver