I’m trying to find duplicates being generated in a particular dataset

My orginal query is SELECT b.admidate, a.token_person_id,
COUNT (DISTINCT(a.token_person_id)) as patientCount
FROM new_alzheimers_agegroup2 a
left join inpatient_mapping b on b.token_person_id=a.token_person_id and a.indexdate=b.disdate

order by a.token_person_id

But i’m finding 1500 duplicates compared to the raw data. How do I build a query that will find duplicates.

SELECT b.admidate, a.token_person_id,
COUNT (DISTINCT(a.token_person_id)) as patientCount
FROM new_alzheimers_agegroup2 a
left join inpatient_mapping b on b.token_person_id=a.token_person_id and a.indexdate=b.disdate

order by a.token_person_id