I'm running a query to see who hasn't signed up for classes, and whenever I do it, it duplicates the student information and displays them twice. Any reason query wise it would be doing this?
Here is the query.
SELECT DISTINCT a.grade, a.lastname, a.firstname, a.sid
FROM aspen a
LEFT JOIN gh g ON a.sid = g.sid
WHERE g.sid IS NULL
order by a.grade, a.lastname, a.firstname
Since you aren't interested in any data from gh
simply use not exists
select grade, lastname, firstname, sid
from aspen a
where not exists (select * from gh where gh.sid = a.sid)
order by grade, lastname, firstname
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