Postgres 15

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CREATE TABLE my_table (
  test_field character varying(255), 
  id int
);

insert into my_table values
('Hello', 2),
(null, 3);

CREATE TABLE

INSERT 0 2

select *
from my_table;

test_field
id

Hello
2

null
3

SELECT 2

SELECT
"id"
FROM my_table
WHERE string_to_array(COALESCE("test_field"::TEXT, 'null'), ',') 
      && REPLACE('{Hello, null}', 'null' , '"null"')::TEXT[]

id

2

3

SELECT 2

SELECT
"id"
FROM my_table
WHERE string_to_array(COALESCE("test_field"::TEXT, 'null'), ',') && '{Hello, "null"}'

id

2

3

SELECT 2