Columns based on SELECT commands can also be calculated, which means they can be derived from other columns. The following query, for example, returns every film’s length, plus 45 minutes:
SELECT Filmtitle, Length + 45 FROM tblFilms
If you do not use AS to specify a column name for a calculated field, SQL Server/MSDE uses the name Expr< n >, with n denoting the column number.
You can use the following query to determine a product’s gross sales, plus value-added tax:
SELECT ProductNr, Description, SalesPrice * 1.16 AS Gross FROM tblProducts
Table 9-1 lists the operators you can use to perform column calculations.