Consolidate SQL Union With JOIN

Question

Let's say I have 2 tables ( bar_helper and bar ). I have a query that retrieves records based on a JOIN between the tables and some condition.

Essentially, my first result set is joined and I want my second one to be unconditional and just based on one table.

SELECT DISTINCT a.barId, b.foo 
FROM bar_helper a 
    JOIN bar b ON a.barId=b.id
WHERE a.color='blue' AND b.type='wood';

This works fine. However, now I need to also get a second set of bar records (unconditional of bar_helper ). I don't want to execute a second query and then merge results. It looks like I can solve this with UNION (not using All bc deduped is fine)

So now my query would be something like.

SELECT DISTINCT a.barId, b.foo 
FROM bar_helper a 
    JOIN bar b ON a.barId=b.id
WHERE a.color='blue' AND b.type='wood'

UNION

SELECT id, foo
FROM bar where magnitude=10;

This seems to work and I get 1 resultset that combines both. Is there a more consolidated way to do this though? Can I just use OR . The JOIN is what's confusing me. I'm looking for something that's like.. "get these first set of results"....."but...also...get these too".

Any insights?

Answer 1

Use EXISTS :

SELECT b.id, b.foo
FROM bar b 
WHERE b.magnitude = 10
   OR 
   (b.type = 'wood' AND EXISTS (SELECT 1 FROM bar_helper a WHERE a.color = 'blue' AND a.barId = b.id))

Answer 2

If you reorganize the logic a little this is just a LEFT JOIN:

SELECT b.id, b.foo
FROM bar b
LEFT JOIN bar_helper a ON b.id = a.barid
WHERE
    b.Magnitude = 10
OR (b.type = 'wood' AND a.color = 'blue')