> For the complete documentation index, see [llms.txt](https://www.mlcompendium.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.mlcompendium.com/data/engineering-intro/patterns.md). # Data Patterns A row that changes over time needs a rule for what the history looks like. The pattern for that is slowly changing dimensions: what to do when a row changes, from keeping nothing to keeping every version. The rule belongs to the warehouse design, not to one pipeline. The same notes are in [Data Warehouse](/data/engineering-intro/database-architecture-and-modeling.md#data-warehouse). The reference is Adatis. [Slowly changing dimensions (SCD)](https://adatis.co.uk/introduction-to-slowly-changing-dimensions-scd-types/) by Adatis: what you can do when the information in your table changes, types 0 through 6. The figure below lays those types out side by side, with the credit to Adatis.

Slowly changing dimensions

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