unlang CONDITIONS and sql query

Hi All I am create stored procedure in postgresql database named "findout_cuncurrent_session_for_a_user_result" that return "Deny" or "Permit" . I need to call this procedure in session section but it not working i check all policy that be explaned in unlang man page but this is not working : session { if ("{%sql:select findout_cuncurrent_session_for_a_user_result ('%{User-Name}','%{NAS-IP-Address}','%{Called-Station-Id}','%{Calling-Station-Id}')}" == "Deny") { update control { Pool-Name := "Exceeded-Concurrent-Session" } } } What is the problem? Do i write sql query write ? (this query is work fine in sql.conf )