Question

In my query I want to get the rows from two different tables descending by their primary keys. They have two different keys so is it possible to be able to do this in one query?

Answer 1

Your question is a little vague. To “get rows from two different tables” you can do a JOIN, or you can do a UNION.

In the case of a JOIN:

SELECT a.id, a.something, b.id, b.something
FROM a
INNER JOIN b ON b.aId = a.id
ORDER BY a.id, b.id

In the case of a UNION:

SELECT id, something
FROM (
    SELECT a.id. a.something FROM a
    UNION 
    SELECT b.id, b.something FROM b
) t
ORDER BY t.id

These are very different, but it seems like one of them will meet your needs.

(Note that UNION by default eliminates duplicates. Use UNION ALL to keep duplicates.)