I have a table where there are two columns like below.
x
value1 DerivedFrom
1 0
2 1
3 2
4 3
5 4
Basically, what it is saying is 1 was new, 2 was derived from 1, 3 was derived from 2 and so on.
I want the out put with 1 as the master key and 2,3,4 and 5 as children.
value1 DerivedFrom
1 0
1 1
1 2
1 3
1 4
Is it achiveble in SQL ? Thanks in advance
Advertisement
Answer
As mentioned in the comment, the simplest way is with an rCTE (recursive Common Table Expression):
--Sample Data
WITH YourTable AS(
SELECT *
FROM (VALUES(1,0),
(2,1),
(3,2),
(4,3),
(5,4))V(value1,DerivedFrom)),
--Solution
rCTE AS(
SELECT YT.value1 as rootValue,
YT.value1,
YT.DerivedFrom
FROM YourTable YT
WHERE YT.DerivedFrom = 0
UNION ALL
SELECT r.rootValue,
YT.value1,
YT.DerivedFrom
FROM YourTable YT
JOIN rCTE r ON YT.DerivedFrom = r.value1)
SELECT r.rootValue AS value1,
r.DerivedFrom
FROM rCTE r;