We have already seen column aliases that allow us to rename a field's name in the query output. But we frequently encounter conditions that require changes to a field value. This is where the concept of a calculated field comes in.
Mathematical Calculations
Any numeric field can be operated upon by mathematical operators we are all familiar with. We can add, subtract, multiply, divide, and even find the remainder of a division operation fairly easily. While the operators supported differ in various implementations, the ones given below should be available across any RDBMS you come across (Table 9-1).
Table ...
