-- Sybase ASE 12.5 for Windows 

create table tmp_test
	(
	id numeric( 3 ) identity,
	time_stamp smalldatetime,
	action_id int,
	usr_id int
	)
go

insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040101',
	 1 ,
	 1 
	)
insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040201',
	 1 ,
	 1 
	)
insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040110',
	 2 ,
	 1 
	)
insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040111',
	 2 ,
	 1 
	)
insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040104',
	 1 ,
	 2 
	)
insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040110',
	 1 ,
	 2 
	)
insert into
	tmp_test
	(
	time_stamp,
	action_id,
	usr_id
	)
values
	(
	'20040201',
	 1 ,
	 2 
	)
go

select
	t1.usr_id,
	t1.action_id,
	min(t1.time_stamp) as min_time_stamp,
	max(t2.time_stamp) as max_time_stamp,
	datediff(dd,min(t1.time_stamp),max(t2.time_stamp)) as max_time_day
from
	tmp_test t1
	inner join
		tmp_test t2
		on
		t1.usr_id = t2.usr_id
		and
		t1.action_id = t2.action_id
group by
	t1.usr_id,
	t1.action_id
go

 --RESULTS 
usr_id	action_id	min_time_stamp	max_time_stamp	max_time_day
 1 	 1 	 2004 - 01 - 01   00 : 00 : 00 	 2004 - 02 - 01   00 : 00 : 00 	 31 
 1 	 2 	 2004 - 01 - 10   00 : 00 : 00 	 2004 - 01 - 11   00 : 00 : 00 	 1 
 2 	 1 	 2004 - 01 - 04   00 : 00 : 00 	 2004 - 02 - 01   00 : 00 : 00 	 28