再帰的なクエリのPostgreSQLのマニュアルをワークアウトするのに問題があり、誰かが以下の提案を提供できる可能性があるかどうか疑問に思う。
これがデータです:
Table "public.subjects"
Column | Type | Collation | Nullable | Default
-------------------+-----------------------------+-----------+----------+--------------------------------------
id | bigint | | not null | nextval('subjects_id_seq'::regclass)
name | character varying | | |
Table "public.subject_associations"
Column | Type | Collation | Nullable | Default
------------+-----------------------------+-----------+----------+--------------------------------------------------
id | bigint | | not null | nextval('subject_associations_id_seq'::regclass)
parent_id | integer | | |
child_id | integer | | |
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ここでは、「被験者」には、多くの親と多くの子供がいます。もちろん、トップレベルで、被験者には両親と底の子供がいない。例えば:
parent_id | child_id
------------+------------
2 | 3
1 | 4
1 | 3
4 | 8
4 | 5
5 | 6
6 | 7
_
私が探しているのは、すべての先祖を取得するためのchild_idとparent_id、すべての子孫で始まります。したがって:
parent_id 1 -> children 3, 4, 5, 6, 7, 8
parent_id 2 -> children 3
child_id 3 -> parents 1, 2
child_id 4 -> parents 1
child_id 7 -> parents 6, 5, 4, 1
_
私が彼らの理にかなっているのに苦労していることについての類似したことの例がたくさんあるようですが、私が試してみることができる提案は歓迎されるでしょう。
被験者1の子供をすべて入手するには、使用できます
WITH RECURSIVE c AS (
SELECT 1 AS id
UNION ALL
SELECT sa.child_id
FROM subject_associations AS sa
JOIN c ON c.id = sa. parent_id
)
SELECT id FROM c;
_
CREATE OR REPLACE FUNCTION func_finddescendants(start_id integer)
RETURNS SETOF subject_associations
AS $$
DECLARE
BEGIN
RETURN QUERY
WITH RECURSIVE t
AS
(
SELECT *
FROM subject_associations sa
WHERE sa.id = start_id
UNION ALL
SELECT next.*
FROM t prev
JOIN subject_associations next ON (next.parentid = prev.id)
)
SELECT * FROM t;
END;
$$ LANGUAGE PLPGSQL;
_
これを試して
--- Table
-- DROP SEQUENCE public.data_id_seq;
CREATE SEQUENCE "data_id_seq"
INCREMENT 1
MINVALUE 1
MAXVALUE 9223372036854775807
START 1
CACHE 1;
ALTER TABLE public.data_id_seq
OWNER TO postgres;
CREATE TABLE public.data
(
id integer NOT NULL DEFAULT nextval('data_id_seq'::regclass),
name character varying(50) NOT NULL,
label character varying(50) NOT NULL,
parent_id integer NOT NULL,
CONSTRAINT data_pkey PRIMARY KEY (id),
CONSTRAINT data_name_parent_id_unique UNIQUE (name, parent_id)
)
WITH (
OIDS=FALSE
);
INSERT INTO public.data(id, name, label, parent_id) VALUES (1,'animal','Animal',0);
INSERT INTO public.data(id, name, label, parent_id) VALUES (5,'birds','Birds',1);
INSERT INTO public.data(id, name, label, parent_id) VALUES (6,'fish','Fish',1);
INSERT INTO public.data(id, name, label, parent_id) VALUES (7,'parrot','Parrot',5);
INSERT INTO public.data(id, name, label, parent_id) VALUES (8,'barb','Barb',6);
--- Function
CREATE OR REPLACE FUNCTION public.get_all_children_of_parent(use_parent integer) RETURNS integer[] AS
$BODY$
DECLARE
process_parents INT4[] := ARRAY[ use_parent ];
children INT4[] := '{}';
new_children INT4[];
BEGIN
WHILE ( array_upper( process_parents, 1 ) IS NOT NULL ) LOOP
new_children := ARRAY( SELECT id FROM data WHERE parent_id = ANY( process_parents ) AND id <> ALL( children ) );
children := children || new_children;
process_parents := new_children;
END LOOP;
RETURN children;
END;
$BODY$
LANGUAGE plpgsql VOLATILE COST 100;
ALTER FUNCTION public.get_all_children_of_parent(integer) OWNER TO postgres
--- Test
SELECT * FROM data WHERE id = any(get_all_children_of_parent(1))
SELECT * FROM data WHERE id = any(get_all_children_of_parent(5))
SELECT * FROM data WHERE id = any(get_all_children_of_parent(6))
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