Expressions that compute values from one or more columns can be used advantageously in the WHERE clause of a query. Any legal arithmetic expression involving columns, constants, functions and arithmetic operators (+, -, * and /) is permitted in a WHERE clause. Parentheses may be used as necessary to define evaluation order.
If null values appear in an expression the result will be null.
The following query is an example of an expression appearing in the WHERE clause of a query:
SELECT pno, weight FROM part WHERE city = "LONDON" AND weight * 2 > 25