How do I transpose multiple rows to columns in SQL - sql

Question

My first time reading a question on here.
I am working at a university and I have a table of student IDs and their supervisors, some of the students have one supervisor and some have two or three depending on their subject.
The table looks like this
ID Supervisor
1 John Doe
2 Peter Jones
2 Sarah Jones
3 Peter Jones
3 Sarah Jones
4 Stephen Davies
4 Peter Jones
4 Sarah Jones
5 John Doe
I want to create a view that turns that into this:
ID Supervisor 1 Supervisor 2 Supervisor 3
1 John Doe
2 Peter Jones Sarah Jones
3 Peter Jones Sarah Jones
4 Stephen Davies Peter Jones Sarah Jones
5 John Doe
I have looked at PIVOT functions, but don't think it matches my needs.
Any help is greatly appreciated.

Answer 1

PIVOT was the right clue, it only needs a little 'extra' :)
DECLARE #tt TABLE (ID INT,Supervisor VARCHAR(128));
INSERT INTO #tt(ID,Supervisor)
VALUES
(1,'John Doe'),
(2,'Peter Jones'),
(2,'Sarah Jones'),
(3,'Peter Jones'),
(3,'Sarah Jones'),
(4,'Stephen Davies'),
(4,'Peter Jones'),
(4,'Sarah Jones'),
(5,'John Doe');
SELECT
*
FROM
(
SELECT
ID,
'Supervisor ' + CAST(ROW_NUMBER() OVER(PARTITION BY ID ORDER BY Supervisor) AS VARCHAR(128)) AS supervisor_id,
Supervisor
FROM
#tt
) AS tt
PIVOT(
MAX(Supervisor) FOR
supervisor_id IN ([Supervisor 1],[Supervisor 2],[Supervisor 3])
) AS piv;
Result:
ID Supervisor 1 Supervisor 2 Supervisor 3
1 John Doe NULL NULL
2 Peter Jones Sarah Jones NULL
3 Peter Jones Sarah Jones NULL
4 Peter Jones Sarah Jones Stephen Davies
5 John Doe NULL NULL
You will notice that the assignment to Supervisor X is done by ordering by the Supervisor-VARCHAR. If you want the ordering done differently, you might want to include an [Ordering] column; then change to ROW_NUMBER() OVER(PARTITION BY ID ORDER BY [Ordering]). Eg an [Ordering] column could be an INT IDENTITY(1,1). I'll leave that as an excercise to you if that's what's really needed.