查詢查找表

Question

的相同值我有一個表：

courseTracker(
     student int 
     courseID int 
) 

我想找到每個學生誰擁有作爲學生「B」

Answer 1

我不確定同一課程，這些的兩個你想要的，所以我包括兩個。

這將返回誰擁有至少一門課程中常見的爲B的學生：

SELECT DISTINCT student FROM coursetracker 
WHERE courseID IN (
    SELECT courseID FROM coursetracker WHERE student = 'B' 
) 

這將返回誰具有完全相同的課程爲B的學生：

SELECT student FROM (SELECT DISTINCT student FROM coursetracker) c 
WHERE NOT EXISTS (
    SELECT * FROM coursetracker c1 
     FULL JOIN coursetracker c2 ON c1.courseId = c2.courseId 
      AND c1.student = c.student AND c2.student = 'B' 
    WHERE c1.courseID IS NULL OR c2.courseID IS NULL 
)