Where, either or not both clause SQL

Question

I am trying to list students who were enrolled in at least one course in Fall quarter or at least one course in the Spring quarter, but not both. I have tried to go at this from different angles but so far I haven't succeeded with any of them. The code that I feel completes this solution would be the following. Any help is appreciated!

SELECT enrolled.StudentID, student.LastName, student.FirstName
   , enrolled.courseID, enrolled.Quarter  
FROM enrolled 
INNER JOIN student ON enrolled.studentID = student.SID
GROUP BY enrolled.StudentID, student.LastName, student.FirstName
   , enrolled.courseID, enrolled.Quarter
HAVING (count(distinct enrolled.Quarter) = 1)

Answer 1

You could use something along the following lines:

 SELECT 
   enrolled.StudentID, student.LastName, 
   student.FirstName, enrolled.courseID, enrolled.Quarter  
 FROM enrolled
 where StudentID in ( 
     SELECT StudentID 
     FROM enrolled where quarter in ( 'fall', 'spring' )
     group by StudentID
     having count(*) = 1 
   )      

Answer 2

Sorry on my phone so not going to be a complete answer.

I would try

Select [what you want]
From students as s
Outer apply
(
Select distinct sid 
From enrolled as e
Where e.sid =s.sid
And quorter = 1
) as q1
Outer apply
(
 Select distinct sid 
From enrolled as e
Where e.sid =s.sid
And quorter = 2
) as q2
Where
((  q1.sid  is null and q2.sid is not null)
Or 
( q1.sid is not null and q2.sid is null))
And (q1.sid is not null and q2.sid is not null)

Answer 3

I'd do a union query.

select yourfields
from enrolled
where studentid in
(select studentid
from enrolled 
where quarter = 'fall'
minus
select studentid
from enrolled 
where quarter = 'spring')

union all
select yourfields
from enrolled
where studentid in
(select studentid
from enrolled 
where quarter = 'spring'
minus
select studentid
from enrolled 
where quarter = 'fall')

Not entirely sure if MySQL supports the keyword minus. Some db's do, some don't. If not, it might support the keyword except.

Answer 4

Stouny's comment was correct, removing quarter from the group by and using an aggregator in the select will work:

SELECT enrolled.StudentID, student.LastName, student.FirstName, enrolled.courseID, max(enrolled.Quarter) as quarter
FROM enrolled 
INNER JOIN student ON enrolled.studentID = student.SID
GROUP BY enrolled.StudentID, student.LastName, student.FirstName, enrolled.courseID
HAVING count(*) = 1

Another approach that won't scale well if you have lots of quarters to check, but works ok for 2:

SELECT enrolled.StudentID, student.LastName, student.FirstName, coalesce(spring.courseID, fall.courseID), coaleasce(spring.Quarter, fall.quarter)  
FROM students
LEFT OUTER JOIN enrolled as spring ON spring.studentId = students.sid and spring.quarter = 'spring'
LEFT OUTER JOIN enrolled as fall ON fall.studentId = students.sid and fall.quarter = 'fall'
WHERE (spring.courseID != NULL and fall.courseID = NULL) OR (spring.courseID ! NULL and fall.courseID != NULL)