Dette er en Relationel Division uden Rester (RDNR) problem. Se denne artikel af Dwain Camps, der giver mange løsninger på denne form for problemer.
Første løsning
SELECT empId
FROM (
SELECT
empID, cc = COUNT(DISTINCT department)
FROM employe
WHERE department IN('Y', 'Z')
GROUP BY empID
)t
WHERE
t.cc = 2
AND t.cc = (
SELECT COUNT(*)
FROM employe
WHERE empID = t.empID
)
Anden løsning
SELECT e.empId
FROM employe e
WHERE e.department IN('Y', 'Z')
GROUP BY e.empID
HAVING
COUNT(e.department) = 2
AND COUNT(e.department) = (SELECT COUNT(*) FROM employe WHERE empID = e.empId)
Uden at bruge GROUP BY
og HAVING
:
SELECT DISTINCT e.empID
FROM employe e
WHERE
EXISTS(
SELECT 1 FROM employe WHERE department = 'Z' AND empID = e.empID
)
AND EXISTS(
SELECT 1 FROM employe WHERE department = 'Y' AND empID = e.empID
)
AND NOT EXISTS(
SELECT 1 FROM employe WHERE department NOT IN('Y', 'Z') AND empID = e.empID
)