srinivas, Pooja is clearly saying that she wants to add a column which RESIDES on the database. She's NOT trying to create a calculated query item.
Lynn is right. On the DB layer of your FM (or whatever you call your data source query subjects layer), right click the concerned query subject, click edit definition, click the test tab and then click test sample at the bottom of the screen. If everything is fine and results come back including your new column from the DB, click ok.
Then go to your model query subject layer, right click the concerned query subject, click edit definition and then drag in the newly added query item from the model query subject. Change the name if needed. Do the whole test thing as above and click ok if everything looks good.