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DataExpert-io / cumulative-table-design

This repository helps teach people how to correctly define and create cumulative tables!
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COALESCE snapshot date #4

Open TommyLiang99 opened 2 weeks ago

TommyLiang99 commented 2 weeks ago

https://github.com/DataExpert-io/cumulative-table-design/blob/7177daa195a4c8b4c08d123d9910f641847bcb94/queries/active_users_cumulated_populate.sql#L51 Don't we need to coalesce the snapshot date as well? What happens if the user appear on day 1 and day 3 but not on day 2. How will we able to retrieve its activity array on day 2 if t.snapshot_date will be null on day 2, so it will be null in the table.

TommyLiang99 commented 2 weeks ago

Actually you need to do something like COALESCE(t.snapshot_date, y.snapshot_date + 1)