尝试在两个表上进行左联接，但只希望右表中的一个

Question

So I have two tables.

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

So, Now I want to do a left join where in I join only one of the matching rows from table 2. THe join will be on Receiver column, and the ID column in each table is different.

I tried left join, and it gave me everything from TABLE 2 (Understandably). I looked at other queries online but got lost.

Can anyone help me with this?

EDIT

Starting query (from OP's comments):

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

Try using a group by to make the Receiver column unique:

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

Answer 2

You can change your left join to a normal join , since you are always expecting a match.

And to limit the matches to a single row, you can use row_number over () , where the order by clause is meaningless, since you don't care which row you are matching to.

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

As you are only interested in one column which is the same for every record, you can use a subquery:

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

(That column being always the same indicates a bad table design however.)

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