postgres insert if not exists

The query first makes a CTE (Common Table Expression) d with the data you want to insert. hope not blackpink Then it makes a CTE t with the token in session that match the token in d (or empty if no match). hope not blackpink Then it uses CTE i to insert the row from d if it has no match in t into session And finally it returns the row from d if it did have a match in t