Question

我有一张桌子：

courseTracker(
        student int
        courseID int
)

我想找到每个与学生'B'具有相同课程的学生

Answer 1

我不确定你想要哪两个，所以我包括了两个。

这将使至少有一门课程的学生回归B：

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

这将返回与B课程完全相同的学生：

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
)

查询查找表的相同值

1 个答案: