what is a specimen test that is top four most commonly given since 4 years ago?
select t1.spec_type_desc from ( select microbiologyevents.spec_type_desc, dense_rank() over ( order by count(*) desc ) as c1 from microbiologyevents where datetime(microbiologyevents.charttime) >= datetime(current_time,'-4 year') group by microbiologyevents.spec_type_desc ) as t1 where t1.c1 <= 4