Question

我不是SQL专家。我正在使用SQL Server 2005，我正试图弄清楚如何构建一个查询，以便它可以满足几个要求。我有两个表定义如下：

Classroom
 - ID
 - DepartmentID
 - TeacherName
 - RoomNumber

Student
 - ID
 - Name
 - ClassroomID

我正在尝试建立一个查询，上面写着“给我部门[x]或部门[y]的教室，这些教室有超过30名学生，并给我部门教室[w]或部门[z]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，我正在尝试以下方法：

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

你需要在由AND连接的前两个布尔表达式周围添加一组parens

应该是

(...) OR
(...)

等

Answer 2

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

Answer 3

试试这个

(SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID) >30

而不是

(SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID > 30)

Answer 4

非常清楚你的parens。

请注意，我又添加了3组parens。

((c.[DepartmentID]=5) AND ((SELECT COUNT(*) FROM Student s WHERE s.ClassroomID=c.ID) > 30)) OR

SQL - 混合AND和OR

4 个答案: