Retrieving the latest row per group from PostgreSQL

In this post I'll show you several approaches you can use if you need to solve tasks along the lines of "retrieve the earliest/oldest/last etc row per group" from your database. I rank them by how performant I found them to be on a made-up dataset I made for this purpose.

I explain what determines the different timings with the help of visualisations showing how the database processes the query internally. As you will see, we will go from hundreds …

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