Querying a jsonb array in postgres - arrays

Question

Table:
CREATE TABLE appointment
(
id bigserial NOT NULL,
date_of_visit timestamp without time zone NOT NULL,
symptoms text[],
diseases text[],
lab_tests text[],
prescription_id bigint NOT NULL,
medicines jsonb,
CONSTRAINT appointment_pkey PRIMARY KEY (id),
CONSTRAINT appointment_prescription_id_fkey FOREIGN KEY (prescription_id)
REFERENCES prescription (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITH (
OIDS=FALSE
);
Insert statement:
INSERT INTO appointment values(
1,
now(),
'{"abc","def","ghi"}',
'{"abc","def","ghi"}',
'{"abc","def","ghi"}',
1,
'[{"sku_id": 1, "company": "Magnafone"}, {"sku_id": 2, "company": "Magnafone"}]')
I am trying to query against a jsonb array type column in postgres. I had some solution in hand which is as below. Somehow it is not working The error is - Cannot extract elements from a scalar.
SELECT distinct(prescription_id)
FROM appointment
WHERE to_json(array(SELECT jsonb_array_elements(medicines) ->>'sku_id'))::jsonb ?|array['1']
LIMIT 2;
Update:
The query runs just fine. There was some unwanted value in the column for some other rows because of which it was not running.

Answer 1

There are rows in the table containing a scalar value in column medicines instead of array.
You should inspect and properly update the data. You can find these rows with this query:
select id, medicines
from appointment
where jsonb_typeof(medicines) <> 'array';
Alternatively, you can check the type of values in this column in the query:
select prescription_id
from (
select distinct on (prescription_id)
prescription_id,
case
when jsonb_typeof(medicines) = 'array' then jsonb_array_elements(medicines) ->>'sku_id'
else null
end as sku_id
from appointment
) alias
where sku_id = '1'
limit 2;
or simply exclude non-array values in where clause:
select prescription_id
from (
select distinct on (prescription_id)
prescription_id,
jsonb_array_elements(medicines) ->>'sku_id' as sku_id
from appointment
where jsonb_typeof(medicines) = 'array'
) alias
where sku_id = '1'
limit 2;