mysql - sql中的交集

Question

我必须在 SQL 中找到 2 个查询中的交集，并且我正在使用 INTERSECTION，但是当我在命令上尝试它时，当我知道有一行属于该类别时，查询不会显示任何结果。 问题如下: 查找同时修读 CIS 类(class)和历史类(class)的学生的全名 这是我的代码:

SELECT student.sid
FROM student
JOIN registration 
ON registration.sid = student.sid
JOIN course 
ON registration.crn = course.crn
WHERE dept= "CIS" 

INTERSECT

SELECT student.sid 
FROM student
JOIN registration 
ON registration.sid = student.sid
JOIN course 
ON registration.crn = course.crn
WHERE dept = "HIS";

Answer 1

这有效

SELECT fName, lName
FROM student
JOIN registration 
ON registration.sid = student.sid
JOIN course 
ON registration.crn = course.crn
WHERE dept= "CIS" 

AND student.sid IN

(SELECT student.sid 
FROM student
JOIN registration 
ON registration.sid = student.sid
JOIN course 
ON registration.crn = course.crn
WHERE dept = "HIS");