Select the first row in a join of two tables in one statement

Question

I need to select only the first row from a query that joins tables A and B. On table B exist multiple records with same name. There are not identifiers in any of the two tab

Answer 1

If you can add to a temp table and then query from that, you can do it in one go.

WITH T AS (temp table select), RN AS (select min row-numbers from T) SELECT T.NAME, T.DATA1, T.DATA2 FROM T INNER JOIN RN on T.row_number = RN.row_number

There are many other ways to write this, but that's how I've been doing similar things.

Answer 2

The tag of this question indicates that it would be a solution for DB2, but this is very similar to MS-SQL server, if so try these solutions:

Using CROSS, it will be possible to display what exists only in both tables

select A.*, B.DATA1, B.DATA2
from A
cross apply (select top 1 * from B where B.name = A.name) B

But it is possible to change to OUTER to display what exists in A without the obligation to exist in B

select A.*, B.DATA1, B.DATA2
from A
OUTER apply (select top 1 * from B where B.name = A.name) B

In the structure of the apply statement, it would also be possible to include an ORDER statement, since there is no indication of the order of exits in table B