Having problems identifying my mistake - sql

Question

The tables which are already created and unmodifiable are Book and Author.
Book (Title, Price, Yeareleased)
Author(AName,btitle,position)
Italized are the keys
and Btitle in Author is a foreign key that references Book(Title).
My SQL query:
select distinct AName
from Author
where position in (2,3) AND position<>1
group by AName
When I run this I get all the authors that have a book in position 2 or 3. Which is what I want but I'm only trying to get those authors which have a position 2 or 3 for all there books.
Essentially returning every author who was in the 2nd or 3rd position in all the books.

Answer 1

Maybe something like this would work:
select distinct AName
from #Author
where position in (2,3)
except
select distinct AName
from #Author
where position not in (2,3)
It makes a set of those authors who are in position 2 and 3 and then removes the ones who has another position.

Answer 2

It is not entirely clear whether someone who co-wrote 2 books and was listed second on one and third on the other should be selected or not. It is simpler to allow it; you can refine the query if you need the more stringent condition.
One way to answer this query makes the key observation that you're interested in authors for whom the count of the books they have written is equal to the count of the books where they are listed as second or third author.
Go for some TDQD — Test-Driven Query Design
Number of books each author wrote
SELECT Aname, COUNT(*) AS BookCount
FROM Author
GROUP BY AName
Number of books each author wrote as second or third author
SELECT Aname, COUNT(*) AS NonLeadAuthorCount
FROM Author
WHERE Position IN (2, 3)
GROUP BY Aname
Join those two where the counts are identical
SELECT X.Aname
FROM (SELECT Aname, COUNT(*) AS BookCount
FROM Author
GROUP BY AName
) AS X
JOIN (SELECT Aname, COUNT(*) AS NonLeadAuthorCount
FROM Author
WHERE Position IN (2, 3)
GROUP BY Aname
) AS Y
ON X.BookCount = Y.NonLeadAuthorCount
An alternative way of looking at is 'the set authors who have written a book in position 2 or 3 minus the set of authors who have written a book where the position is neither 2 nor 3'. For this, see the answer by jpw.

Answer 3

Trying to write standard SQL:
SELECT AName FROM (
SELECT
AName,
COUNT(*) AS count_all,
(SELECT COUNT(*) FROM Author AS aa WHERE aa.AName = a.AName AND position=2) AS count_2,
(SELECT COUNT(*) FROM Author AS aa WHERE aa.AName = a.AName AND position=3) AS count_3,
FROM Author AS a
GROUP BY AName
) AS t
WHERE count_all = count_2
OR count_all = count_3
I hope this work for you.

Answer 4

Try this:
select AName from Author where position=2 OR position=3 group by AName;

Answer 5

Try adding
and AName not in (select AName from Author where position != 2 and position != 3
Or something like that...