Select parent if all children meet criteria

Question

I have tables set up like so:

Parent
------
id, ...

Child
-----
id, parent_id, x, y

I want to find the Parents, or the distinct parent_id(s),

Answer 1

You can use NOT EXISTS

SELECT id 
FROM Parent p
WHERE NOT EXISTS
(
   SELECT 1 FROM Child c
   WHERE c.parent_Id = p.id
   AND c.x <> c.y
)

Edit: Here's the sql-fiddle: http://sqlfiddle.com/#!3/20128/1/0

Answer 2

This is what you need?

  select id from parent where id not in(
    select parent_id from chile 
    where x<>y
    group by parent_id)

Answer 3

Should join 2 tables first because the parents does not have children that will satisfy

And should add index for pa_id column

SELECT DISTINCT pa.id 
FROM pa INNER JOIN c ON c.pa_id = pa.id 
WHERE NOT EXISTS ( SELECT 1 FROM c WHERE c.parent_Id = p.id and c.x <> c.y )