tell me the four most common medical diagnoses in a year before?
select d_icd_diagnoses.short_title from d_icd_diagnoses where d_icd_diagnoses.icd9_code in ( select t1.icd9_code from ( select diagnoses_icd.icd9_code, dense_rank() over ( order by count(*) desc ) as c1 from diagnoses_icd where datetime(diagnoses_icd.charttime,'start of year') = datetime(current_time,'start of year','-1 year') group by diagnoses_icd.icd9_code ) as t1 where t1.c1 <= 4 )