query a jsonb array in a select of another query - postgresql

Question

I have a user table with a column favorites that is a jsonb
favorites:
[
{
"id_doc:": 9,
"type": "post"
},
{
"id_doc": 10,
"type": "post"
}
]
And I have another table posts where I want to make a query by id and this id must be in the fields id_doc in the favorites user
select * from posts where id in (select favorites -> id_doc from users )
This is the schema
CREATE TABLE dev.users
(
id integer NOT NULL GENERATED BY DEFAULT AS IDENTITY ( INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1 ),
firstname character varying COLLATE pg_catalog."default" NOT NULL,
lastname character varying COLLATE pg_catalog."default" NOT NULL,
email character varying COLLATE pg_catalog."default" NOT NULL,
password character varying COLLATE pg_catalog."default" NOT NULL,
favorites jsonb[],
CONSTRAINT users_pkey PRIMARY KEY (id),
CONSTRAINT email_key UNIQUE (email)
)
WITH (
OIDS = FALSE
)
TABLESPACE pg_default;
ALTER TABLE dev.users
OWNER to postgres;
CREATE TABLE dev.posts
(
id integer NOT NULL DEFAULT nextval('dev.posts_id_seq'::regclass),
title character varying COLLATE pg_catalog."default" NOT NULL,
userid integer NOT NULL,
description character varying COLLATE pg_catalog."default" NOT NULL,
CONSTRAINT posts_pkey PRIMARY KEY (id)
)
WITH (
OIDS = FALSE
)
TABLESPACE pg_default;
ALTER TABLE dev.posts
OWNER to postgres;
How can I do this?
Thank you

Answer 1

There are other ways to accomplish this, but I prefer using CTEs for clarity. Please let me know in the comments if you have questions about what this does.
with elements as (
select jsonb_array_elements(favorites) as favitem
from users
), fav_ids as (
select distinct (favitem->>'id_doc')::int as id_doc
from elements
)
select p.*
from posts p
join fav_ids f on f.id_doc = p.id
;
Update
Since the column is defined as jsonb[] rather than json, we need to unnest() instead of jsonb_array_elements():
with elements as (
select unnest(favorites) as favitem
from users
), fav_ids as (
select distinct (favitem->>'id_doc')::int as id_doc
from elements
)
select p.*
from posts p
join fav_ids f on f.id_doc = p.id
;