This query shows the number of users for each day. I use it on PokerDIY to see how many new users joined - I leave the sorting to the SQLView module so I can click on the col headings...
SELECT DAY(CreatedDate) as 'Day', DATENAME(m , CreatedDate) as Month, YEAR(CreatedDate) as 'Year', COUNT(*) As 'New Users'
FROM Users U
INNER JOIN UserPortals UP ON UP.UserID = U.UserID
WHERE PortalID = 6
AND Authorised = 1
GROUP BY DAY(CreatedDate), DATENAME(m , CreatedDate), MONTH(CreatedDate), YEAR(CreatedDate)