SQL join query result issue - sql

Question

I have two tables one is Friends table and other table is user profile table (all user related information e.g. firstname, lastname etc) both has relation among them
Friend table (It has two entries for every user for e.g. the first two rows)
Now i want to display names of users from above table which will look like below
so in the output i want to remove duplicates which is not working for me
my query
select distinct u.FirstName + ' ' + u.LastName As UserName,
(select distinct firstname + ' ' + lastname from UserProfiles where id = uw.friendid) as FriendName
from UserFriends as uw left join userprofiles as u
on u.id = uw.userid

Answer 1

You need to join UserProfiles twice on UserFriends since there are two columns are dependent on it.
SELECT a.ID,
f.FirstName + ' ' + f.LastName FriendName,
u.FirstName + ' ' + u.LastName UserName
FROM UserFriends a
INNER JOIN UserProfiles f
ON a.FriendID = f.ID
INNER JOIN UserProfiles u
ON a.UserID = u.ID
INNER JOIN UserFriends dup
ON a.FriendID = dup.UserID
AND dup.FriendID = a.UserID
AND a.ID > dup.ID
SQLFiddle Demo

Answer 2

I would suggest that you have to use CTE to eliminate the duplicates from the beggining(that can be done by self joining the table). I have managed to reproduce your scenario, so if you adjust the query a bit, you will be able to obtain the desired result
with cte as
(select
t1.id as a_id
,t1.friendID as a_friendID
,t1.userID as a_userID
,t2.id as b_id
,t2.friendID as b_friendID
,t2.userID as b_userID
from #temp t1
left join #user t2 on t1.id+1=t2.id
),
cte2 as
select
a_id
,a_userID
,a_friendID
from cte t1
where a_friendID = (select b_friendID from cte t2 where t2.b_id= t1.b_id-1)
)
select firstname+ ' '+lastname as FriendName
,firstname+ ' '+lastname as UserName
from cte2 uw
left join UserProfiles u on uw.a_userID=u.ID and uw.a_friendID=u.id