SQL statement to get column based on ID from same table

Question

The table is like so:

ID	Name	SupervisorID
1	John	NULL
2	Michael	NULL
3	David	1

SupervisorID is a foreign key of ID. So, David's SupervisorID of 1 refers to John.

I want to write a statement that retrieves just Name and Supervisor Name, where applicable. So the result-set should look like this:

Name	Supervisor
John	NULL
Michael	NULL
David	John

It seems like it should be simple but I can't work it out.

Thank you!

Answer 1

Simply do a self LEFT JOIN:

select t1.name, t2.name
from tablename t1
left join tablename t2 on t2.ID = t1.SupervisorID

(Doing a LEFT JOIN to also return people without a supervisor.)