este problema se llama Relational Division
SELECT boy_id
FROM boys_chocolates
WHERE chocolate_id IN ('$string')
GROUP BY boy_id
HAVING COUNT(DISTINCT chocolate_id) = ? -- <<== number of chocolates specified
ejemplo:
SELECT boy_id
FROM boys_chocolates
WHERE chocolate_id IN (1,2,3,4)
GROUP BY boy_id
HAVING COUNT(DISTINCT chocolate_id) = 4
sin embargo, si el chocolate_id
es único para cada boy_id
, DISTINCT
la palabra clave es opcional.
SELECT boy_id
FROM boys_chocolates
WHERE chocolate_id IN (1,2,3,4)
GROUP BY boy_id
HAVING COUNT(*) = 4
ACTUALIZACIÓN 1
...Quiero elegir chicos de la mesa que tengan exactamente los chocolates que menciono. Ni más ni menos...
SELECT boy_id
FROM boys_chocolates a
WHERE chocolate_id IN (1,2,3,4) AND
EXISTS
(
SELECT 1
FROM boys_chocolates b
WHERE a.boy_ID = b.boy_ID
GROUP BY boy_id
HAVING COUNT(DISTINCT chocolate_id) = 4
)
GROUP BY boy_id
HAVING COUNT(*) = 4