Question

I want to use left outer join like this:

    SELECT ...
FROM Table1
LEFT OUTER JOIN
(SELECT only e.g. 3rd record... , SomeField FROM Table2) tbl2
  ON Table1.SomeField = tbl2.SomeField

How can I do that, if I need the subquery to select not just the 3rd record from Table2, but the 3rd record among the Table2 records that have SomeField = Table1.SomeField?
Thanks.

Answer 1

If this is sql server 2005 or newer, you might use row_number():

LEFT JOIN
(
   select *
     from
     (
       select *,
              row_number() over (order by something) rn
         from Table2
        where Table2.Column = Table1.Column
     ) a
    where a.rn = 3
) a

Unfortunately you need to nest it a level deeper because you cannot use row_number in a condition directly.

EDIT:

My bad – i didn’t really notice the join part. If you want to join derived table, use this:

LEFT JOIN
(
   select *,
          row_number() over (partition by SomeField order by something) rn
     from Table2
) tbl2
  ON Table1.SomeField = tbl2.SomeField
 AND tbl2.rn = 3

Note: you need ORDER BY in row_number() to keep things consistent.