Комбинацията PHP/MySQL води до мислене в термини на клиентски ad-hoc заявки.
Аз би го имплементирал със записана така някак:
CREATE TABLE #TmpRequiredSkills(skill_id INT NOT NULL)
-- INSERT #TmpRequiredSkills
-- SELECT Code
-- FROM dbo.fn_sys_Split(@TextParamWithIDsConcat, NULL) s
INSERT #TmpRequiredSkills
SELECT 1 UNION ALL
SELECT 2 UNION ALL
SELECT 3
SELECT e.*
FROM employee AS e
JOIN (
SELECT es.employee_id
FROM employee_skill AS es
WHERE es.skill_id IN (SELECT skill_id FROM #TmpRequiredSkills)
GROUP BY es.employee_id
HAVING COUNT(*) = (SELECT COUNT(*) FROM #TmpRequiredSkills)
) AS filter
ON e.employee_id = filter.employee_id
(MS-SQL)
cheers,
</wqw>