Looping Thru A Table And Updating The Contents

Hello, Its hard trying to explain this.

I have 3 tables

Table 1 is where the users are stored, each user has a username and a userrank

Table 2 is where the points that decides the userrank are stored

Table 3 contains the available userranks like this

 

Table 1 (user_list) looks briefly like this:
username nvarchar(20),
userrank int, -- Reference to Table3 id
... alot more fields

Table 2 (settings_profile) looks like this:
username nvarchar(20),
total_active_points int,
... some more fields

Table 3 (data_ranks) looks like this:
id int primary key auto inc,
rankname nvarchar(20),
min_pts int,
max_pts int

 

Points get added to table 2 whenever they do something that generates points on the site. Points also get withdrawn every 7 days, so a user can only collect points for 7 days, on the 8th day, all points he earned on the 1st day is reduced from the current points with this code:

WHILE (SELECT @username = username, @id = id, @temp1 = ap_sentmails, @temp2 = ap_createdthreads, @temp3 = ap_createdanswers, @temp4 = ap_signguestbook, @temp5 = ap_blogcomment, @temp6 = ap_createblogentry, @temp7 = ap_profilefirsttime, @temp8 = ap_profilephoto, @temp9 = ap_activateguestbook, @temp10 = ap_addnewfriend, @temp11 = ap_superguruvote, @temp12 = ap_forumtopicvote, @temp13 = ap_labervote, @temp14 = ap_funstuffitemvote, @temp15 = ap_movievote, @temp16 = ap_actorvote, @temp17 = ap_money_new WHERE (created < Dateadd(dd, -7, @todaysdate))
BEGIN
SET @sum = 0
SET @sum = @temp1 + @temp2 + @temp3 + @temp4 + @temp5 + @temp6 + @temp7 + @temp8 + @temp9 + @temp10 + @temp11 + @temp12 + @temp13 + @temp14 + @temp15 + @temp16 + @temp17
UPDATE settings_profile SET total_active_points = total_active_points - @sum WHERE (username = @username)
DELETE FROM konto_daylist WHERE (id = @id)
END

Now my question is this, i want to loop thru the table A, collect all usernames inside of it, then run it against table b and table c to determine the current rank of the user.
Something like this...

DECLARE @username nvarchar(20)
DECLARE @pts int, @rank int

...something that starts a loop thru table A (user_list) and get the username into @username...

SELECT @pts = total_active_points  FROM settings_profile WHERE (username = @username)
-- Determine the rank here, by compairing the points the user have against the pointstabel in table data_ranks
SELECT @rank = id FROM data_ranks WHERE (pts_min => @pts AND pts_max < @pts)
UPDATE user_list SET rank = @rank WHERE (username = @username)

...next persion in the loop...

This SP runs once a day and will first reduce the points from 8days ago, then it will run thru all the users and determine their new rank...

But how do i loop thru all the users? with a cursor?