How to perform a LEFT JOIN in SQL Server between two SELECT statements?

I have two SELECT statements in SQL Server like these:

(SELECT [UserID] FROM [User])
(SELECT [TailUser], [Weight] FROM [Edge] WHERE [HeadUser] = 5043)

I want to perform a LEFT JOIN between these two SELECT statements on [UserID] attribute and [TailUser] attribute. I want to join existent records in second query with the corresponding records in first query and NULL value for absent records. How can I do this?

4 Answers

SELECT * FROM
(SELECT [UserID] FROM [User]) a
LEFT JOIN (SELECT [TailUser], [Weight] FROM [Edge] WHERE [HeadUser] = 5043) b
ON a.UserId = b.TailUser

SELECT [UserID] FROM [User] u LEFT JOIN (
SELECT [TailUser], [Weight] FROM [Edge] WHERE [HeadUser] = 5043) t on t.TailUser=u.USerID

select *
from user
left join edge
on user.userid = edge.tailuser
and edge.headuser = 5043

Try this:

SELECT user.userID, edge.TailUser, edge.Weight
FROM user
LEFT JOIN edge ON edge.HeadUser = User.UserID
WHERE edge.HeadUser=5043

OR

AND edge.HeadUser=5043

instead of a WHERE clause.