Operand deve conter 1 coluna - MySQL NOT IN
SELECT * from campaigns WHERE id not in
(SELECT
e.id_campaign, d.name, d.frequency, d.country, d.referral, d.bid, d.status, COUNT(e.id) AS countcap
FROM campaigns d
LEFT JOIN served e
ON d.id = e.id_campaign
WHERE
d.status = 'Active'
GROUP BY e.id_campaign
HAVING
countcap < d.frequency)
Eu recebo o erro "Operando deve conter 1 coluna" - mas preciso da COUNT (e.id)