Avoid arithmetic expressions
Do not use an arithmetic expression as an operand to compare to a column in a row selection predicate. The optimizer does not use an index on a column compared to an arithmetic expression. While this technique might not cause the column index to become unusable, it prevents any estimates and possibly the use of index scan-key positioning. The primary thing that is lost is the ability to use and extract any statistics that might be useful in the optimization of the query.
For example, when using SQL, specify the following:
… WHERE SALARY > 16500 instead of
… WHERE SALARY > 15000*1.1