mysql - SQL 检查两个表是否具有特定 ID 的相同数据

Question

假设我有一个名为 Catalog 的表，如下所示:

Course Number  CourseName   CourseDsc   PreReq
   1028          CS146      Data S...   1005
   1028          CS146      Data S...   2000
   1028          CS146      Data S...   2003

还有另一个名为 PreviousCourses 的表，如下所示:

Username     PrevCoursesID      Grade
admin          1005              A
admin          2000              A

现在，该用户管理员不满足类(class) CS146 的先决条件，因为他具有三个先决条件中的两个(1005 和 2000)，但缺少先决条件 2003。我的查询设置方式是它检查 PreviousCourses 是否是 Catalog 的子集。基本上，如果满足特定类(class)的任何先决条件，则允许用户注册该类(class)。我希望我的查询的行为是，只有满足特定类(class)目录中的所有先决条件，用户才能注册。 我的查询尝试:

"Select PrevCoursesID, Grade from PreviousCourses where "
                        + "Grade <= 'D' AND "
                        + "PrevCoursesID IN (Select PreReq from Catalog where CourseNumber = '" + courseID + "') AND"
                        + " Username = '" + currentUser + "'";

更新:刚刚尝试了此查询，但似乎不起作用

         SELECT CATALOG.prereq, previouscourses.grade
         FROM CATALOG LEFT JOIN PREVIOUSCOURSES ON   
         CATALOG.prereq=PREVIOUSCOURSES.PREVCOURSESID AND   
    PREVIOUSCOURSES.GRADE<='D' WHERE PREVIOUSCOURSES.USERNAME='ADMIN' 
AND CATALOG.COURSENUMBER='1028'

Answer 1

这些是用户可以参加的类(class):

DECLARE @UserName varchar(255) = 'admin'


    SELECT c.[Course Number]
    FROM Catalog c
    GROUP BY c.[Course Number]
    HAVING COUNT(1) =  (SELECT COUNT(DISTINCT pc.PreReq) 
                        FROM PreviousCourses pc
                        WHERE pc.Username = @UserName 
                              AND c.PreReq = pc.PrevCoursesID 
                              AND pc.Grade IN ('A', 'B', 'C', 'P', 'Pass')
           OR MAX(ISNULL(c.PreReq, 0)) = 0
    ORDER BY c.[Course Number]

(这是 SQL Server)