Question

I’m using 2 tables

Let’s say (There’s more to these tables but that’s just a very simple view of it)

Table1 is
sID   ResearchPaperID 
1     A1
2     A1
3     A1
4     A1


Table2 is
sID    Name
1     Person1
2     Person2
3     Person3
4     Person4

What I need to do is find people who are associated with(co-wrote) Person1’s papers but not show Person1 in the output.

Currently I have something like

SELECT Table2.sID, Table1.sID
FROM Table2, Table1
WHERE Table2.sID = Table1.sID
AND Table2.Name = 'Person1'

which would give me everything that Person1 has done.

This is a homework question been stuck on it for a while now.

Can’t use sub-queries as well.
Sorry I should mention no use of inner joins, outer joins, left/right joins, natural joins.

It’s not supposed to be much harder than what I have above just using basic commands..

[EDIT]
Output would be something like this

ResearchPaperID    Name
A1                 Person2
A1                 Person3
A1                 Person4

I want to find people that are co-writers of papers of person1 but not show person1 in the output

Answer 1

Solution, without subqueries and JOIN’s:

select distinct t3.sID, t3.ResearchPaperID
from Table1 t1, Table2 t2, Table1 t3
where t1.sID = t2.sID and t2.Name = 'Person1'
  and t1.ResearchPaperID = t3.ResearchPaperID
  and t3.sID <> t2.sID       -- this restriction is the one that removes the 'Person1'