Displaying the Document Window
The document window can be configured to display either tabbed documents, or a multiple-document interface (MDI) environment. In tabbed document mode, which is the default, multiple documents show as tabs along the top of the document window.
To view the default tabbed document layout
On the main toolbar, click Database Engine Query. In the Connect to Database Engine dialog box, click Connect.
In Object Explorer, right-click your server and then click New Query. In this case, the Query Editor uses the connection information of the Registered Server.
Note how the windows appear as tabs on the document window.