Това трябва да гарантира, че има и двете
WHERE id IN
(
SELECT clientid
FROM campaigns
WHERE status IN ('L')
)
AND id IN
(
SELECT clientid
FROM campaigns
WHERE status IN ('P')
)
Или дори опитайте Подзаявки с EXISTS
WHERE EXISTS
(
SELECT clientid
FROM campaigns
WHERE status IN ('L')
AND clientid = client.id
)
AND EXISTS
(
SELECT clientid
FROM campaigns
WHERE status IN ('P')
AND clientid = client.id
)