Hi! I've already asked this question a month ago - it remains unanswered. Dare to repeat since this issue is rather important for me. So. When I invoke select 1 where 5 in (null) everything is Ok, though when I try select 1 where 5 in (select null) I get ERROR: failed to find conversion function from "unknown" to integer. Is it desired behavior or subject to change in future versions of PG? I realize my simplified example looks radiculous while it came from reality. Sometimes my engine generates SQL queries does not know correct type and unable to cast, while PostgreSQL should have all information required. Thanks. -- Best regards Ilja Golshtein ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend