Postgres query with JSONField on array

Question

I am new to Postgres, and try to build a SQL query that can retrieve a Key/Value dictionary pair in an array [] from table table_b and use it in the WHERE clause on finding matching tag_name and tag_value returning the object_uuid

The original tags on table_b were stored as JSONField() in Django -> Postgres and not sure how that would work in array on extracting each one out.

Question: How do we build a SQL query can traverse each name and value in table_b.tags and then use it to match it on table_a?

table_a

tag_name	tag_value	object_uuid
foobar	coffee	aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee
hello	world	3dd98cb6-978c-44b0-92fd-403032a7cb1f
key_one		81bba637-4156-42b2-a2c0-ae5dd23ed695

table_b

id	object_uuid	tags
3	00000000-1111-2222-3333-444444444444
4	99999999-8888-7777-6666-555555555555
271		[{"name": "foobar", "value": "coffee"}, {"name": "hello", "value": "world"}]

I think I come with this


SELECT
    id,
    object_uuid,
    name,
    value
FROM table_b b,
     jsonb_to_recordset(b.tags) AS (name TEXT, value TEXT)

id	object_uuid	name	value
271		foobar	coffee
271		hello	world

score 0 · Answer 1 · answered Aug 26 '22 at 05:54

You can join using the @> operator after building an array with the tagname and value:

select b.id, b.object_uuid, a.tag_name, a.tag_value
from table_b b
  join table_a a on b.tags @> jsonb_build_array(jsonb_build_object('name', a.tag_name, 'value', a.tag_value));

This assumes that table_b.tags is a jsonb column (which it really should be). If it's not, you need to cast it b.tags::jsonb

Postgres query with JSONField on array

1 Answers1