Question

我想要获得ID为444111110的学生可以注册的课程。可以注册的课程是没有先决条件或课程的课程他已经取得的先决条件并在其中取得了成绩。

学生退学的课程也必须展示，所以他可以再次注册。它将在等级栏中给出“W” 不得展示学生所选课程和课程。如果他已经参加了这门课程，那么它将在成绩栏中获得“U”。

#COURSE_ID   PREREQUISITE_COURSE_ID
CS111        NULL
CS211        CS111
CS244        CS311
CS244        CS211
CS244        CS111
CS311        CS211
CS311        CS111

# STUDENT_ID  COURSE_ID  DATEREGISTERED  EnrollToken  GREADE
444111110     CS111      2005-03-10      5            A
444111110     CS211      2005-03-10      7            A+
444111111     CS111      2005-03-10      6            W

# COURSE_ID  COURSE_NAME           TERM  CREDITS_HOUR  SEATS_LEFT
CS111        Intro. to CS          1     3             50
CS211        Intro. to PS          2     3             50
CS244        Adcanced Application  4     3             50
CS311        Introduction to OOB   3     3             50

我试过这个查询 SELECT DISTINCT C.COURSE_ID, C.COURSE_NAME, C.SEATS_LEFT FROM ENROLLMENT E, PREREQUISITE P, COURSES C WHERE C.COURSE_ID NOT IN (SELECT COURSE_ID FROM ENROLLMENT WHERE STUDENT_ID = '444111110' AND GREADE !='U') AND P.PREREQUISITE_COURSE_ID IN (SELECT COURSE_ID FROM ENROLLMENT WHERE STUDENT_ID = '444111110' AND GREADE !='W'); 但它返回CS244和CS311给id为444111110的学生，而它应该只返回CS311。对于没有注册任何课程或退出CS111的第一门课程的学生，也不会返回任何内容。

是否有可能的方法来检查学生是否将所有必修课程都纳入其中？并且有一种方法可以为没有注册任何课程的学生修复该查询，以证明他们可以注册CS111，其先决条件是NULL吗？

提前致谢。

Answer 1

，试试这个

select course_ID, COURSE_NAME, SEATS_LEFT from Courses
where course_ID in (select course_ID from Enrollment where grade ='W')
or course id in (select course_id from Prerequisites where prerequisite_course_id in (select course_ID from Enrollment where grade != 'W')

Answer 2

SELECT COURSE_ID,COURSE_NAME,SEATS_LEFT FROM Courses WHERE Course_ID NOT IN (
    SELECT Course_ID FROM prerequisite WHERE PREREQUISITE_COURSE_ID IN 
    (SELECT Course_ID FROM Courses WHERE Course_ID NOT IN 
    (SELECT Course_ID FROM Enrollment WHERE Student_ID = '444111110' AND GREADE NOT IN ('U', 'F', 'W') ) ) ) AND Course_ID NOT IN 
    (SELECT Course_ID FROM Enrollment WHERE Student_ID = '444111110' AND (GREADE = 'U' OR GREADE NOT IN ('F', 'W') )  );

我要感谢我的导师为我解决这个问题。

SQL列值必须存在于两个表

2 个答案: