Top Medical Codes by Demographics

Write a query using window functions to identify the top three most frequent medical codes for each patient demographic group in a given dataset.

Use the supplied patient, medical event, and code reference tables. Exclude events without a valid patient, code, or demographic group. Return at most three codes per demographic group.

Output

1. One row per demographic group and medical code, with columns demographic_group, medical_code, occurrence_count, and code_rank.
2. Include only the top three codes in each group, ranking higher frequencies first and breaking ties by medical_code ascending.
3. Order by demographic_group ascending, then code_rank ascending.