refactor(snowflake): revise and expand

knowledge base/data warehouse.md

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+# Data warehouse
+
+Centralized repository that stores large amounts of data from various sources.<br/>
+It possibly stores the data in structured and organized ways that are optimized for data analysis and generation of
+reports and insights.
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
+## TL;DR
+
+Operational systems upload the data, which may require cleansing.
+
+The two main workflows for data warehouse systems are:
+
+- _Extract, Transform, Load_ (ETL).
+- _Extract, Load, Transform_ (ELT).
+
+<!-- Uncomment if used
+<details>
+  <summary>Setup</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Usage</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+- [What is a data warehouse?]
+- [Snowflake]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+[snowflake]: snowflake/README.md
+
+<!-- Files -->
+<!-- Others -->
+[What is a data warehouse?]: https://www.ibm.com/think/topics/data-warehouse