Question

I have a table with columns like

entityID, entityName, parentID

How can I write a query to return all the levels of parents for an entity as to return something like

childentityname, parentlevel1name, parentlevel2name, parentLevel3name and so on

I am not a SQL ninja by any means. Is this possible? If so, how?

I’m using Microsoft SQL Server DB.

Answer 1

A recursive CTE is what you need look here (EDIT: Only in SQL SERVER 2005+)

Something along the lines of:

WITH recurse_cte (entityID,entityName, parentID, Level)
AS
(
-- Anchor member definition
    SELECT e.entityID,e.entityName, e.parentID,
        0 AS Level
    FROM self_joined AS e
        UNION ALL
-- Recursive member definition
    SELECT e.entityID,e.entityName, e.parentID,
        Level + 1
     FROM self_joined AS e
    INNER JOIN recurse_cte AS cte
        ON e.entityID = cte.parentID
)

select * from recurse_cte