SQL-基于同一表中的多个条目进行选择？

Question

If my tables are setup like this:

Apply: studentID, cName

Student: studentID, sName

How can I list studentID and sName from Student where there are entries in Apply that have:

Apply.studentID = Student.studentID AND Apply.cName = "College1"

AND

Apply.studentID = Student.studentID AND Apply.cName = "College2"

Ultimately, what I am trying to do is list the students that have applied to both colleges with cNames "College1" and "College2"..

Answer 1

By doing two subqueries, one to get the studentIDs that applied to College1 and another for College2 you can ensure that the students returned from Student have studentIDs that exist in both of the subquery result sets.

SELECT sName
FROM Student 
WHERE studentID IN (
    SELECT DISTINCT studentID FROM Apply WHERE cName='College1'
)
AND studentID IN (
    SELECT DISTINCT studentID FROM Apply WHERE cName='College2'
)

Answer 2

You can check if it EXISTS with both criteria:

select * from Student s
where exists 
(select * from Apply a where a.StudentId = s.StudentId and a.cName = 'College1') and
exists 
(select * from Apply a where a.StudentId = s.StudentId and a.cName = 'College2');

Answer 3

You can use CTE to avoid duplicated codes.

with
    cte
as
(
    select
        studentID
    from
        [Apply]
    where
        cName   in('College1', 'College2')
)
select
    s.sName
from
    cte
inner join
    Student s
on
    cte.studentID = s.studentID;