Random username

[billy_111]

Hey,

I am taking users through a registration section on a client website. When the submit button is clicked, i need to create a ransom username for the user and insert it into the database table. I am doing a simple INSERT as so...

                $insert = "INSERT INTO tbl_members(username, password, email, gender, postcode, DOB, education, date_added) VALUES 

                (

// Insert values here

                )";

                $add_member = mysql_query($insert); 

Now the username needs to be a random username, and cannot be the same as any other usernames in the same table..

How can i do this?

Regards