# SQL

> Selected Engineer ApS work demonstrating SQL — the achievements that prove it.

- [Led the development, deployment, and support of over 30 GIS projects, demonstrating expertise in PostgreSQL, Bash, Python, JavaScript, GDAL, ArcGIS, PostGIS, and Mapbox technologies.](https://advisory.engineer.company/portfolio/led-the-development-deployment-and-support-of-over-35/)
- [Built the loyalty and reputation system — 67 functions over a 31‑table ledger, with leagues, badges and a redemption shop — taking a row lock on the balance to close the double‑spend window.](https://advisory.engineer.company/portfolio/built-the-loyalty-and-reputation-system-105/)

<https://advisory.engineer.company/categories/sql/>