PostgreSQL unnest with empty array

Question

I use postgreSQL 9.1. In my database there is a table which looks like

id | ... | values
-----------------------
1  | ... | {1,2,3}
2  | ... | {}

Answer 1

This works on Postgres 10 also:

SELECT id, UNNEST(CASE WHEN "values" <> '{}' THEN "values" ELSE '{null}' END)