Confused Joins

I am using this query to create a single transactions from data that is distributed over several databases. So essentially i have created several variable tables and now I have to join them together.
So what I wanted to have happen was display all rows from temptalbel and then join the other tables to create one transaction row. The problem that occurs is within the where statement and I dont understand why. In some cases, you can have two instances of x but y will be different. In that case the joins work perfectly. In the event that there are only a single instance of x associated with a single instance of y this join does not work. Can anyone help me understand why this is happening?

select somedata, somedata, somedata, somedata
From kpi..temptablel l
left outer join @temps s on l.x = s.x
left outer join @tempf f on l.x = f.x
left outer join kpi..temptablee e on l.x = e.x
left outer join @tempn n on l.x = n.x

where l.y = s.y and l.y = f.y and l.y = e.y and l.y = n.y


The Yak Village Idiot