A computed column is computed from an expression that can use other columns in the same table. The expression can be a noncomputed column name, constant, function, variable, and any combination of these connected by one or more operators. The expression cannot be a subquery.
For example, in the AdventureWorks sample database, the TotalDue column of the Sales.SalesOrderHeader table has the definition: TotalDue AS Subtotal + TaxAmt + Freight.
