mysql - 编写一个 sql 查询来查找在 R128 房间中遇到的类的名称

Question

考虑以下架构:

Student(snum, sname, major,level)

Class(cname, meets-at,room, fid)

Faculty(fid, fname, depname)

Enrolled(snum, cname)

编写一个 SQL 查询来查找不在 R128 房间内学生人数最少的所有类(class)的名称(与所有其他类(class)相比)。

Answer 1

试试这个

SELECT E.cname, Count(snum) 
    FROM Enrolled E
    GROUP BY E.cname
    HAVING Count(snum) in(
            SELECT TOP 1  Count(snum) cnameCount
            FROM Enrolled E
            JOIN Class C
            ON E.cname=C.cname
            WHERE C.room!='R128'
            GROUP BY c.CName
            ORDER BY Count(snum)
            )