SQL Server Management Studio allows you to easily comment out a portion of your script.
To comment out a portion of your script
Use your mouse to select the text WHERE LastName = 'Sanchez'.
On the Edit menu, point to Advanced, and then click Comment Selection. The selected text is commented out with dashes (--).
In addition to using the Edit menu, you can comment or uncomment a selected portion of your script by using either of the following methods:
Click the buttons on the SQL Editor toolbar.
Press CTRL+K and CTRL+C to comment the text, or press CTRL+K, CTRL+U to uncomment the text.