stupid "SELECT" :-(...

Hi

I have a table like that:
      addr_ip       date
      127.0.0.1    20050512140758 
      127.0.0.1    20050512143522 
      127.0.0.1    20050512143710 
      127.0.0.1    20050512203349 
      24.60.19.142 20050512203407 
      24.60.19.142 20050512203409 
      24.60.19.142 20050512203409 
      127.0.0.1    20050512215434 
      24.60.19.142 20050512215451 
      127.0.0.1    20050512225606 
      127.0.0.1    20050512225617 
      24.60.19.142 20050512225712 

And I would like a result like this:
addr_ip   date           min( sup.date)
127.0.0.1 20050512140758 20050512143522 
127.0.0.1 20050512143522 20050512143710 
127.0.0.1 20050512143710 20050512203349 
127.0.0.1 20050512203349 20050512203407 
127.0.0.1 20050512215434 20050512215451 w
127.0.0.1 20050512225606 20050512225617 w
127.0.0.1 20050512225617 20050512225712 w
24.60.19.142 20050512203407 20050512203409 
24.60.19.142 20050512203409 20050512215434 w
24.60.19.142 20050512215451 20050512225606 w

As you see I'm trying to write in one record the interval of 2 following pos
itions for the same @IP. I tried this after hours of efforts but it doesn't 
work well:
SELECT tab.addr_ip, tab.date, min( sup.date ) 
FROM visit tab, visit sup
WHERE tab.date < sup.date
GROUP BY tab.date
ORDER BY tab.addr_ip, tab.date

Do you have any other solution, sources that would help me?

Nick
Thanks.