You could update all of the empty ones with the same data using,
mysql_query("UPDATE table SET uploads = '232', channelviews = '576', videoviews = '91231' WHERE uploads = ''");
Or, fetch all the empty ones, and loop through them and update them individually.
This way you can set the data for each row, instead of having them all the same.
$fetch_empty = mysql_query("SELECT id FROM table WHERE uploads = '' OR channelviews = ''");
while($empty = mysql_fetch_array($fetch_empty))
// Generate a random number here... use the variable in the query below?
mysql_query("UPDATE table SET uploads = 'xx', channelviews = 'xx', videoviews = 'xx' WHERE id = '" . $empty['id'] . "'");