Creating Dynmic system identification number with table name and record creation time

CREATE OR REPLACE FUNCTION f_sys_id (p_table IN VARCHAR2, p_time VARCHAR2)
   RETURN VARCHAR2
IS
   sql_stmt   VARCHAR2 (150);
   RESULT     VARCHAR2 (20);
BEGIN
   sql_stmt :=
         'SELECT '
      || TO_CHAR (SYSDATE, 'RRRRMMDDHH24MISS')
      || '||'
      || ' lpad(COUNT(*)+1,6,0) from '
      || p_table
      || ' where '
      || 'to_char ('
      || p_time
      || ','
      || '''rrrrmmddhh24miss'
      || ''')='
      || TO_CHAR (SYSDATE, 'RRRRMMDDHH24MISS');

   EXECUTE IMMEDIATE sql_stmt
                INTO RESULT;

   RETURN RESULT;
END;
/

Email Address Validation in Oracle Forms

SELECT (CASE
           WHEN REGEXP_LIKE ('jsd.jf@hotmail.com', '^\w+(\.\w+)*+@\w+(\.\w+)+$')
              THEN 'true'
           ELSE 'false'
        END
       ) emai_validity
  FROM DUAL;