我有一张像这样的桌子pupil_teachers
+------+----------+------------+
| id | pupil_id | teacher_id |
+------+----------+------------+
| 1 | 100 | 200 |
| 2 | 101 | 200 |
| 3 | 102 | 200 |
| 4 | 102 | 201 |
| 5 | 101 | 201 |
| 6 | 101 | 202 |
| 7 | 103 | 200 |
+------+----------+------------+
查询将是检索学生100,101和102共有的所有教师。所以在这种情况下,它只是id为200的老师。
Pupil 103也有ID为200的老师,但不是查询的一部分,我只想查询学生100,101和102。
所以它将从以下开始:
SELECT teacher_id
FROM pupil_teachers
WHERE
我真的不知道下一步该往哪里去。显然以下是不正确的
SELECT teacher_id
FROM pupil_teachers
WHERE pupil_id IN (100, 101, 102)
这是使用Group By
和Having
子句的一种方法
SELECT teacher_id
FROM pupil_teachers
WHERE pupil_id IN (100, 101, 102)
Group by teacher_id
Having Count(Distinct pupil_id) = 3
其他方式
SELECT teacher_id
FROM pupil_teachers
Group by teacher_id
Having Count(Case when pupil_id = 100 then 1 end) > 0
AND Count(Case when pupil_id = 101 then 1 end) > 0
AND Count(Case when pupil_id = 102 then 1 end) > 0