Prueba esto:
SELECT *
FROM tablename
WHERE keywordId IN (1, 12)
GROUP BY articleId
HAVING COUNT(*) = 2;
Consulte la DEMOSTRACIÓN DE SQL FIDDLE
Prueba esto:
SELECT *
FROM tablename
WHERE keywordId IN (1, 12)
GROUP BY articleId
HAVING COUNT(*) = 2;
Consulte la DEMOSTRACIÓN DE SQL FIDDLE