Incident age 'grid'

Content

I need to create a report which shows the age of an incident, using the field incidents.c$sla_start

It would be arranged as below:

Days Open:	1	2-7	8-14	15-21	22+
	4	1	9	6	12

I'd hoped to use date_diff, so:

count(distinct if( date_diff(sysdate(),incidents.c$sla_start) <86401, incidents.i_id) )

Should give me the "upto one day old" figures, but what about the rest of the columns? Can you use "between" in an IF statement?