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This article mainly explains "how to achieve grouping aggregation in partition". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to achieve grouping aggregation in partition".

Select * from (select o.order_id, o.user_id, o.amount_money, o.order_date, o.update_date row_number () over (partition by o.order_id, o.user_id order by o.update_date desc) RANK from order o) tmp where tmp.RANK = 1

Example (when the business database processes to the data warehouse every day, it is not reprocessed):

Order_iduser_idamount_moneyorder_dateupdate_date11202020-09-222020-09-2311202020-09-222020-09-2432402020-09-222020-09-2342502020-09-222020-09-23

Unfiltered query results:

Order_iduser_idamount_moneyorder_dateupdate_daterank11202020-09-222020-09-23211202020-09-222020-24132402020-09-222020-09-23142502020-09-222020-09-231

Query results after filtering (where tmp.RANK = 1):

Order_iduser_idamount_moneyorder_dateupdate_daterank11202020-09-222020-09-24132402020-09-222020-09-23142502020-09-222020-09-231

Note: this grouping aggregation is not very time-consuming and is almost the same as without this windowing function.

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