ETL on Morten Ankerstjerne

Repeat last known value

Fri, 18 Jul 2025 00:00:00 +0000

Demo scripts below.

Disclaimer: This technique is by no means something I have come up with, I’ve just needed it enough times that I figured I might as well put it into my own words, for future reference.

Background

Suppose you have a collection of time series data, recording some status or other measurement at a point in time.

In an OLTP system we probably don’t want to repeat the same value every time we take a measurement, or we may only record changes made to a ledger when they occur.

Stop auto-shrinking your staging database

Thu, 05 Jun 2025 00:00:00 +0000

Background

If you’ve worked with data warehouse development on Microsoft SQL Server, you have probably had a run-in with your SAN-admin at some point, complaining about the size of your databases, and asking if you can do some cleanup to free up disk space.

What often ends up happening is, you take look at the database files and realize there’s a lot of free space that could be released, especially if you have a database dedicated to staging transformed data, before loading it into data marts.