Question

如何通过其ID和标题（来自表格＆＃39;考试＆＃39;）选择所有考试，学生（表格＆＃39;成绩＆＃39;）尚未撰写？< / p>

表：成绩

+--------------+----+----
|student_number|e_id| ...
+--------------+----+----
|888075        |1   | ...
|888075        |2   | ...
|888075        |4   | ...
|637020        |2   | ...
+--------------+----+----

表：考试

+----+------+
|e_id|title |
+----+------+
|1   |exam 1|
|2   |exam 2|
|3   |exam 3|
|4   |exam 4|
+----+------+

在这种特殊情况下，我希望学生888075得到以下输出：

+--+------+
|id|title |
+--+------+
|3 |exam 3|
+--+------+

我只需要反向选择：

SELECT e.e_id as id, e.title as title
FROM grades g
LEFT JOIN exams e
ON g.e_id = e.e_id
WHERE g.student_number = '888075'

Answer 1

您的查询已关闭 - 只需反转联接并相应地检查null：

SELECT e.e_id as id, e.title as title
FROM exams e
   LEFT JOIN grades g ON g.e_id = e.e_id
      AND g.student_number = '888075'
WHERE g.e_id IS NULL

Answer 2

您需要选择那些不在e_id的学生参与的e_id。

SELECT aa.e_id AS id, aa.title
FROM exams AS aa
WHERE e_id NOT IN (
    SELECT e_id
    FROM grades
    WHERE student_number = '888075'
    GROUP BY e_id
);

OR

SELECT aa.e_id AS id, aa.title
FROM exams AS aa
WHERE e_id NOT IN (
    SELECT DISTINCT e_id
    FROM grades
    WHERE student_number = '888075'
);

OR

SELECT aa.e_id AS id, aa.title 
FROM exams AS aa 
WHERE NOT EXISTS (
    SELECT e_id 
    FROM grades AS bb
    WHERE aa.e_id = bb.e_id AND bb.student_number = '888075'
);

MySQL查询根据不在另一个表

2 个答案: