Tyto dva dotazy nedáváte do souvislosti:
SELECT X
FROM A
WHERE (
SELECT COUNT(DISTINCT y)
FROM b
WHERE b.x = a.x
) > 2
Tyto dva dotazy nedáváte do souvislosti:
SELECT X
FROM A
WHERE (
SELECT COUNT(DISTINCT y)
FROM b
WHERE b.x = a.x
) > 2