Question

If I need to fetch rows from table A with a matching tag in table B, I’ll just do a simple JOIN ON/WHERE B.name=X. But MySQL will then only return the row from A and the matching tag from B.

What do I do if I want to retrieve all from table A that has a match in table B, and at the same time retrieve all from table B that are linked to the row in table A.

A:
a.id
1
2
3

B: 
b.id   | b.a_id   | b.name
1      | 1        | foo
2      | 1        | bar
3      | 1        | derp
4      | 2        | foo
5      | 2        | derp
6      | 3        | bar

A search for "foo" should then return
a.id   | b.id     | b.a_id   | b.name
1      | 1        | 1        | foo
1      | 2        | 1        | bar
1      | 3        | 1        | derp
2      | 4        | 2        | foo
2      | 5        | 2        | derp

Appreciate any help I can get. Thanks!

Answer 1

SELECT a.id, b.id, b.name FROM a 
RIGHT JOIN b ON (a.id = b.a_id) 
WHERE a.id IN (SELECT b.a_id FROM b WHERE b.name = 'foo')

I think this is what you are looking for. Might not be the most performant solution, but I hope it will work.

Edit:

SELECT a_new.id, b.id, b.name FROM 
    (SELECT b.a_id FROM b WHERE b.name = 'foo') AS a_new
RIGHT JOIN b ON (a_new.id = b.a_id)

I don’t think it’ll get any better than this, basically you don’t need to query the table a anymore; you fetch all rows from b that match ‘foo’, then join those with all relating items.