> For the complete documentation index, see [llms.txt](https://gchandra.gitbook.io/data-warehousing/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gchandra.gitbook.io/data-warehousing/data-warehousing-concepts/dimensional-modelling/galaxy-schema.md).

# Galaxy Schema

Essentially, Galaxy schema can be derived as a collection of star schemas interlinked and completely normalized to avoid redundancy and inaccuracy of data. It is also called **Fact Constellation Schema.**

Let's combine the above two Star Schemas.

<figure><img src="https://2629735788-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F3G2NQEHaUSzehWzaKvXK%2Fuploads%2F2hJLQM4J9AcTbO7PtvWx%2Fdw_galaxy_schema_01.png?alt=media&amp;token=2a2f644d-b941-495c-ae65-25060d1a1399" alt=""><figcaption></figcaption></figure>

#### Advantages

* Minimum or no redundancy as a result of Normalization.
* This is a flexible Schema, considering the complexity of the system.

#### Disadvantages

* Working on this schema is tedious, as Schema and database systems' complexity makes it more intricate.
* Data retrieval is done with multi-level joins combined with conditional expressions.
* The number of levels of normalization is expected, depending on the depth of the given database.