1. In Object Explorer, right-click the table with columns for which they want to specify a computed column and click Design (Modify in SP1 or earlier).
The table opens in Table Designer.
2. Select the column for which they want to specify a computed column formula.
3. In the Column Properties tab, expand the Computed Column Specification property.
4. In the (Formula) child property, type the expression for this column in the grid cell to the right. For example, ColumnOne * ColumnTwo.
5. Indicate whether the data is persisted by choosing Yes or No from the drop-down for the Is Persisted child property.The new computed column specification is assigned to the column in Table Designer after developers click outside the grid cell or use the TAB key to move to another grid cell and changes are stored in the database when they save their changes in Table Designer.