嘗試在兩個表上進行左聯接，但只希望右表中的一個

Question

所以我有兩個桌子。

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，現在我想做一個left join ，在該聯接中，我僅聯接表2中的匹配行之一。聯接將在Receiver列上，並且每個表中的ID列都不同。

我嘗試了左聯接，它給了我表2中的所有內容（理解）。 我在網上查看了其他查詢，但迷路了。

誰能幫我這個？

編輯

開始查詢（根據OP的評論）：

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

嘗試使用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

您可以將left join更改為普通join ，因為您一直期待匹配。

為了將匹配項限制為單行，可以使用row_number over () ，其中order by子句是沒有意義的，因為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

因為您只對每條記錄都相同的一列感興趣，所以可以使用子查詢：

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

（但是，該列始終相同，這表示表設計不正確。）

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