What's the version of pgsql? postgres=# show server_version; server_version ---------------- 8.1.0 (1 row) postgres=# CREATE OR REPLACE FUNCTION foo (v_s1 varchar, v_s2 varchar) postgres-# RETURNS varchar AS $$ postgres$# BEGIN postgres$# RETURN v_s1 || '\\' || v_s2; postgres$# END; postgres$# $$ LANGUAGE plpgsql; CREATE FUNCTION postgres=# SELECT foo ('pgsql', 'hackers'); foo --------------- pgsql\hackers (1 row) Regards, William ZHANG