У мене є цей SQL:
CREATE TABLE test(id SERIAL PRIMARY KEY, data JSONB);
INSERT INTO test(data) VALUES
('{"parent":null,"children":[2,3]}'),
('{"parent":1, "children":[4,5]}'),
('{"parent":1, "children":[]}'),
('{"parent":2, "children":[]}'),
('{"parent":2, "children":[]}');
Це дало б:
id | data
----+--------------------------------------
1 | {"parent": null, "children": [2, 3]}
2 | {"parent": 1, "children": [4, 5]}
3 | {"parent": 1, "children": []}
4 | {"parent": 2, "children": []}
5 | {"parent": 2, "children": []}
Коли це робиться нормальним для багатьох, це показало б щось таке:
SELECT *
FROM test x1
LEFT JOIN test x2
ON x1.id = (x2.data->>'parent')::INT;
id | data | id | data
----+--------------------------------------+----+-----------------------------------
1 | {"parent": null, "children": [2, 3]} | 2 | {"parent": 1, "children": [4, 5]}
1 | {"parent": null, "children": [2, 3]} | 3 | {"parent": 1, "children": []}
2 | {"parent": 1, "children": [4, 5]} | 4 | {"parent": 2, "children": []}
2 | {"parent": 1, "children": [4, 5]} | 5 | {"parent": 2, "children": []}
5 | {"parent": 2, "children": []} | |
4 | {"parent": 2, "children": []} | |
3 | {"parent": 1, "children": []} | |
Як приєднатися на основі дітей (використовуючи LEFT JOIN
чи WHERE IN
)? Я спробував:
SELECT data->>'children' FROM test;
?column?
----------
[2, 3]
[4, 5]
[]
[]
[]
SELECT json_array_elements((data->>'children')::TEXT) FROM t...
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
SELECT json_array_elements((data->>'children')::JSONB) FROM ...
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
SELECT json_to_record((data->>'children')::JSON) FROM test;
ERROR: function returning record called in context that cannot accept type record
HINT: Try calling the function in the FROM clause using a column definition list.
SELECT * FROM json_to_record((test.data->>'children')::JSON);
ERROR: missing FROM-clause entry for table "test"
LINE 1: SELECT * FROM json_to_record((test.data->>'children')::JSON)...
LINE 4: LEFT JOIN LATERAL json_array_elements(p.data->'children') ... ^ HINT: No function matches the given name and argument types. You might need to add explicit type casts.