Postgres - Remove NULL values from a json array - postgresql

Question

I'm building a JSON ARRAY from a table which has a JSON column and non-JSON columns.
Here is my sample data and query:
create table check_details(SHORT_NAME VARCHAR, UNIQUE_NO JSON,STATUS VARCHAR);
insert into check_details values('Anu','{"ID":"1e699-76af2"}','REJECTED');
select json_agg(json_strip_nulls(
json_build_object('Name',SHORT_NAME,
'IDS',
jsonb_build_array(case SIGN(position('ACCEPTED' in STATUS) ) when 1 then UNIQUE_NO::jsonb->>'ID' else json_typeof(NULL::json) end)
)))
from check_details;
I am getting this result:
[{"Name":"Anu","IDS":[null]}]
But I do not want to get "IDS":[null] part in my result when the value of the key IDS is NULL.
How can I achieve this result:
[{"Name":"Anu"}]
When IDS has a valid value, it has to be an array. Hence using jsonb_build_array.

Answer 1

This is because you are placing the result of your CASE statement in a JSON array, so it's a non-empty array containing a JSON null rather than null JSON value.
So you would need to stop that being an array if you want the NULL to be stripped:
SELECT
json_strip_nulls(
json_build_object(
'Name',
short_name,
'IDS',
CASE SIGN(position('ACCEPTED' IN status) )
WHEN 1 THEN (unique_no::jsonb->>'ID')::text
ELSE NULL
END
)
)
FROM
check_details;
json_strip_nulls
------------------
{"Name":"Anu"}
(1 row)
Note that json_strip_nulls() doesn't remove null values from JSON arrays.
Edit:
But as you require non-null values to show as an array, move the jsonb_build_array() function into the case statement
SELECT
json_strip_nulls(
json_build_object(
'Name',
short_name,
'IDS',
CASE SIGN(position('ACCEPTED' IN status) )
WHEN 1 THEN jsonb_build_array((unique_no::jsonb->>'ID')::text)
ELSE NULL
END
)
)
FROM
check_details;