In Oracle`s dialect of SQL (and in PL/SQL), the NVL function lets you substitute a value when a null value is encountered. In comparison to COALESCE NVL evaluates all arguments before execution: BEGIN END; ORA-06501: PL/SQL: program error ORA-06512: at line 6 ORA-06512: at line 9 http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions105.....