SQL tutorial-Field calculations
SQL allows you to calculate the fields of a table. The basic
arithmetic operations to calculate the fields are addition(+),
subtraction(-), multiplication(*), and division(/).
SELECT ProID,UnitPrice*Qty AS Subtotal
Note: We use the AS keyword to assign the new name(Subtotal) to the new
field that derive from the calculation of other fields. This is called
aliasing the field name.