Dear list,
In reference to the message below posted on the 'pgsql-hackers' list regarding 'iterative' queries,
could anyone help me write the queries that return all full and all partial paths from the root?
Sincerely,
Aryé.
--http://archives.postgresql.org/pgsql-hackers/2008-02/msg00642.php
CREATE TABLE department (
id INT PRIMARY KEY,
parent_department INT REFERENCES department,
name TEXT
);
INSERT INTO department VALUES (0, NULL, 'ROOT');
INSERT INTO department VALUES (1, 0, 'A');
INSERT INTO department VALUES (2, 1, 'B');
INSERT INTO department VALUES (3, 2, 'C');
INSERT INTO department VALUES (4, 2, 'D');
INSERT INTO department VALUES (5, 0, 'E');
INSERT INTO department VALUES (6, 3, 'F');
INSERT INTO department VALUES (7, 5, 'G');
--select * from department
--delete from department
This will represent a tree structure of an organization:
ROOT ---> A ---> B ---> C ---> F
| |
| +----> D
|
+-----> E ---> G
--If you want to extract all departments "under" A, you could use a recursive query:
WITH RECURSIVE subdepartment AS
(
--
SELECT * FROM department WHERE name = 'A'
UNION ALL
-- recursive term referring to "subdepartment"
SELECT d.* FROM department AS d, subdepartment AS sd
--WHERE d.id = sd.parent_department
WHERE d.parent_department = sd.id
)
SELECT * FROM subdepartment;
This will return A, B, C, D and F.
