SQL - 混合 AND 和 OR

Question

我不是 SQL 专家。我正在使用 SQL Server 2005，我正在尝试弄清楚如何构造一个查询，以便它可以满足多种要求。我有两个表定义如下:

Classroom
 - ID
 - DepartmentID
 - TeacherName
 - RoomNumber

Student
 - ID
 - Name
 - ClassroomID

我正在尝试构建一个查询，“给我部门 [x] 或部门 [y] 中超过 30 名学生的教室，并给我部门 [w] 或部门 [z] 中的教室有超过 40 名学生。我对如何在我的 SQL 中正确混合 AND 和 OR 感到困惑。目前，我正在尝试以下操作:

SELECT
  c.RoomNumber,
  c.TeacherName
FROM
  Classroom c
WHERE
  c.[DepartmentID]=5 AND (SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID > 30) OR
  c.[DepartmentID]=6 AND (SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID > 30) OR
  c.[DepartmentID]=7 AND (SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID > 40) OR
  c.[DepartmentID]=8 AND (SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID > 40)

我做错了什么？谢谢!

Answer 1

SELECT  c.id
FROM    Classroom c
JOIN    Students s
ON      s.Classroom = c.Id
WHERE   DepartmentID IN ('X', 'Y', 'W', 'Z')
GROUP BY
        c.id, c.DepartmentID
HAVING  COUNT(*) >= CASE WHEN DepartmentID IN ('X', 'Y') THEN 30 ELSE 40 END