An arithmetic expression combines arithmetic operators with:
    numeric values, numeric host language variables, and/or numeric
    database fields. When you use an arithmetic expression in a
    statement, Oracle Rdb calculates the value associated with the
    expression and uses that value when executing the statement.
    Therefore, an arithmetic expression must be reducible to a value.
    If either operand of an arithmetic expression is a null value,
    the resulting value is also null.

  (B)0arith-expr =

  qwq> numeric-value    qwqqwqq> + qqwqqwq> numeric-value    qwqqq>
   tq> numeric-host-var qu  tqq> - qqu  tq> numeric-host-var qu
   mq> numeric-db-field qj  tqq> * qqu  mq> numeric-db-field qj
                            mqq> / qqj