訪問查詢查找所有鏈接匹配的所有記錄

Question

表格：

tblStudents:
ID, Student Name
1, John
2, Mark
3, Fred

tblEnrolledSubjects:
ID, Student ID, Subject ID, Score
1, 1, 1, 75
2, 1, 2, 75
3, 1, 3, 75
4, 1, 4, NULL
5, 2, 1, 75
6, 3, 1, 75
7, 3, 2, 80
8, 3, 3, 85

tblSubject:
ID, Subject Name
1, Maths
2, English
3, Science
4, History

我想返回所有學科得分都超過（例如70分）的不同學生。 選擇[學生姓名]

學生可以注冊1個或多個科目。 如果學生甚至有一門學科沒有達到要求的分數，則不應列出他們。

從他上面的數據我希望看到

Mark
Fred

SQL查詢將對此做什么？

Answer 1

如果NULL值對您不利，那么

SELECT tblStudents.[Student Name]
FROM tblEnrolledSubjects RIGHT JOIN tblStudents 
    ON tblEnrolledSubjects.[Subject ID] = tblStudents.ID
GROUP BY tblStudents.[Student Name]
HAVING (Min(tblEnrolledSubjects.[Score])>=70);

Answer 2

SELECT t.Studentname
  FROM tblStudents t JOIN
      (select count(*) cnt, min(nz(score,0)) minscore, StudentID
         FROM tblEnrolledSubjects
     GROUP BY StudentID) s
   ON t.Studentid = s.studentid
WHERE minscore>=70 --if mark is greater than or equal to 70