Commenting and Uncommenting Code in SQL Server Management Studio

To comment out lines of code in SQL Server Management Studio (SSMS) Query Window, select lines of code you want to comment out and hit the keyboard shortcut ‘CTRL+K’ followed by ‘CTRL+C’.
You can also select the lines of code and press the ‘Comment out the selected lines.’ button:

You can comment out selected lines of code from the menu bar:
Edit -> Advanced -> Click ‘Comment Selection’

To uncomment lines of code in SQL Server Management Studio (SSMS) Query Window, select lines of code you want to uncomment and hit the keyboard shortcut ‘CTRL+K’ followed by ‘CTRL+U’.
You can also select the lines of code and press the ‘Uncomment the selected lines.’ button:

You can uncomment selected lines of code from the menu bar:
Edit -> Advanced -> Click ‘Uncomment Selection’