Is there any way to send a recursive query in SQL?
Given the end node id, I need all the rows up to the root node (which has parentid = NULL) ordered by level. E.g. if I have something like:
nodeid | parentid
a | NULL
b | a
c | b
after querying for end_node_id = c, I'd get something like:
nodeid | parentid | depth
a | NULL | 0
b | a | 1
c | b | 2
(Instead of the depth I can also work with the distance to the given end node)
The only (and obvious) way I could come up with is doing a single query per row until I reach the parent node.
Is there a more efficient way of doing it?
Ended up with the following solutions (where level is the distance to the end node)
Oracle, using hierarchical queries (thanks to the info provided by @Mureinik):
SELECT IDCATEGORY, IDPARENTCATEGORY, LEVEL
FROM TNODES
START WITH IDCATEGORY=122
CONNECT BY IDCATEGORY = PRIOR IDPARENTCATEGORY;
Example using a view so it boils down to a single standard SQL query (requires >= 10g):
CREATE OR REPLACE VIEW VNODES AS
SELECT CONNECT_BY_ROOT IDCATEGORY "IDBRANCH", IDCATEGORY, IDPARENTCATEGORY, LEVEL AS LVL
FROM TNODES
CONNECT BY IDCATEGORY = PRIOR IDPARENTCATEGORY;
SELECT * FROM VNODES WHERE IDBRANCH = 122 ORDER BY LVL ASC;
http://sqlfiddle.com/#!4/18ba80/3
Postgres >= 8.4, using a WITH RECURSIVE Common Table Expression query:
WITH RECURSIVE BRANCH(IDPARENTCATEGORY, IDCATEGORY, LEVEL) AS (
SELECT IDPARENTCATEGORY, IDCATEGORY, 1 AS LEVEL FROM TNODES WHERE IDCATEGORY = 122
UNION ALL
SELECT p.IDPARENTCATEGORY, p.IDCATEGORY, LEVEL+1
FROM BRANCH pr, TNODES p
WHERE p.IDCATEGORY = pr.IDPARENTCATEGORY
)
SELECT IDCATEGORY,IDPARENTCATEGORY, LEVEL
FROM BRANCH
ORDER BY LEVEL ASC
Example using a view so it boils down to a single standard SQL query:
CREATE OR REPLACE VIEW VNODES AS
WITH RECURSIVE BRANCH(IDBRANCH,IDPARENTCATEGORY,IDCATEGORY,LVL) AS (
SELECT IDCATEGORY AS IDBRANCH, IDPARENTCATEGORY, IDCATEGORY, 1 AS LVL FROM TNODES
UNION ALL
SELECT pr.IDBRANCH, p.IDPARENTCATEGORY, p.IDCATEGORY, LVL+1
FROM BRANCH pr, TNODES p
WHERE p.IDCATEGORY = pr.IDPARENTCATEGORY
)
SELECT IDBRANCH, IDCATEGORY, IDPARENTCATEGORY, LVL
FROM BRANCH;
SELECT * FROM VNODES WHERE IDBRANCH = 122 ORDER BY LVL ASC;