Answer 1

Answer 2

Answer 3

SELECT *
FROM
    (
    SELECT *,
        CASE
        WHEN type = 'Classroom' THEN 1
        WHEN type = 'Computer laboratory' THEN 2
        WHEN type = 'Lecture Hall' THEN 3
        WHEN type = 'Auditorium' THEN 4
        END AS ClassTypeValue
    FROM rooms
    ) t
ORDER BY ClassTypeValue, maxppl, roomID

这是我使用的最终查询。谢谢大家帮助我并向我解释。