How to delete only one row from non unique set of rows in Postgres?

Question

I have this table

create table order_details(
    id_of_product integer,
    id_of_person text
)

both fields are not unique. How to delete one row from the table with specified id_of_product and id_of_person

for example i need to delete one row with id of 6 P.S person is the same for this set of rows

Answer 1

You can use system column ctid to specify particular row, even if it has no unique values.

WITH u AS 
(
    SELECT distinct on (id_of_product, id_of_person) id_of_product, id_of_person, ctid 
    FROM order_details
)
DELETE FROM order_details 
WHERE id_of_product=6 AND id_of_person='ey...' AND ctid IN (SELECT ctid FROM u)