How to assign a JSON variable with row_to_json in PostgreSQL - json

Question

I'm trying to create an annonymous function in PostgreSQL to create mock data for an application.. I would like to do a SELECT query first (to get data from a random charter) and convert all the rows into a JSON with row_to_json, then assign the result into a variable of type JSON.
I need this charter information so I can add it into bookings table.
This is not working, I think I don't know how to associate the result of the select with the variable previously created; I'm getting the error that charterData is null and I would like to know how I can achieve this..
This is the annonymous func in SQL:
BEGIN;
DO $$
DECLARE charterData JSON;
DECLARE bookingId INTEGER;
BEGIN
SELECT row_to_json(t) INTO charterData FROM (select charter_id, name from charters) t WHERE charter_id = 1;
INSERT INTO bookings (charter, yacht, email, date, guests, total, start_hour, end_hour, hotel, arrival_date) values (charterData, '{"test":1}', 'a', '12/10/1995', 8, '78', '123', '123', '123', '123')
RETURNING booking_id INTO bookingId;
END $$;
COMMIT;
Table charter:
Table "public.charters"
Column | Type | Collation | Nullable | Default
-------------+-------------------+-----------+----------+----------------------------------------------
charter_id | integer | | not null | nextval('charters_charter_id_seq'::regclass)
name | character varying | | not null |
description | character varying | | not null |
sail_hours | integer | | not null |
Indexes:
"charters_pk" PRIMARY KEY, btree (charter_id)
"name_charter" UNIQUE CONSTRAINT, btree (name)
Referenced by:
TABLE "bookings" CONSTRAINT "charters_bookings_fk" FOREIGN KEY (charter) REFERENCES charters(name) ON DELETE CASCADE
TABLE "pricing" CONSTRAINT "charters_pricing_fk" FOREIGN KEY (charter_id) REFERENCES charters(charter_id) ON DELETE CASCADE
Bookings table:
Table "public.bookings"
Column | Type | Collation | Nullable | Default
----------------+-------------------+-----------+----------+----------------------------------------------
booking_id | integer | | not null | nextval('bookings_booking_id_seq'::regclass)
charter | json | | not null |
yacht | json | | not null |
email | character varying | | not null |
date | date | | not null |
guests | integer | | not null |
total | numeric | | not null |
start_hour | character varying | | not null |
end_hour | character varying | | not null |
alcohol | character varying | | |
transportation | character varying | | |
others | character varying | | |
arrival_date | character varying | | |
hotel | character varying | | |
Indexes:
"bookings_pk" PRIMARY KEY, btree (booking_id)
"end_hour" UNIQUE CONSTRAINT, btree (end_hour)
"start_hour" UNIQUE CONSTRAINT, btree (start_hour)
Foreign-key constraints:
"charters_bookings_fk" FOREIGN KEY (charter) REFERENCES charters(name) ON DELETE CASCADE
"yachts_bookings_fk" FOREIGN KEY (yacht) REFERENCES yachts(name) ON DELETE CASCADE
Referenced by:
TABLE "bookings_extra" CONSTRAINT "bookings_extra_fk" FOREIGN KEY (booking_id) REFERENCES bookings(booking_id) ON DELETE CASCADE

Answer 1

Okay I have found the answer... Was kinda silly but maybe this answer will help someone
BEGIN;
DO $$
DECLARE charter JSON;
DECLARE bookingId INTEGER;
BEGIN
charter := (SELECT row_to_json(t) FROM (SELECT charter_id, name FROM charters) t WHERE charter_id = $1);
INSERT INTO bookings
(charter, yacht, email, date, passengers, total, start_hour, end_hour, hotel, arrival_date, charter_price)
values (charter, '{"test":1}', 'a', '12/10/1995', 8, '78', '123', '123', '123', '123', '132')
RETURNING booking_id INTO bookingId;
END $$;
COMMIT;