使用 SQL 查找更换医疗服务地点的客户

Question

I wish to identify those customers who MOST RECENTLY switched where they received their medical care over a two year period. I would like to find the last two transactions per customer over the two year period where the diagnosis code is the same but site of service is different .

For example, member 1 has visited both their physician's office and the outpatient facility many times in the two year period, but I am only interested in the last two transactions where they have switched site of service for the same diagnosis code.

As an example my data is structured as followed:

MEMBER_ID DIAGNOSIS_CD  DATE        SITE_OF_SERVICE
1         A             April       Physician
1         A             May         Physician
2         A             May         Home Infusion
1         B             May         Physician
1         A             July        Outpatient
1         A             August      Physician
1         A             September   Physician
1         A             October     Outpatient

Any help with solving this would be greatly appreciated.

I am using Sybase IQ.

Answer 1

You can use:

select
  member_id
from (
  select
    *,
    row_number() 
      over (partition by member_id, diagnosis_cd order by date desc) as rn
  from t
) x
where rn <= 2
group by member_id
having min(site_of_service) <> max(site_of_service)