Dear Sri:
When a table contains a column that references another column in that same
table, it is called a self-reference. That can be accomplished in a query
with a JOIN to the same table. As your "linking" column HEAD can be NULL,
indicating no reference (as it the top of a hierarchy) it will need to be a
LEFT JOIN (or a RIGHT JOIN, but I generally avoid those, prefering to start
at the top and work down.)
SELECT T1.[Name], T2.[Name] AS Head
FROM YourTable T1
LEFT JOIN YourTable T2
ON T2.ID = T.Head
A complete hierarchy can be produced as well:
A
A B
A B C
A B C D
Don't know if that would ever become interesting for you.
Tom Ellison
