SQL for GIS¶

Goal: Get fluent in SQL for attribute queries — the language behind every "Select by Attributes" and Definition Query in ArcGIS Pro.

This is the roadmap entry. The full chapter is in SQL for GIS.

Why SQL?¶

You don't need to be a database engineer. But every GIS analyst writes SQL WHERE clauses every day:

• "Select features where STATE = 'GA'"
• "Filter to incidents in the last 30 days"
• "Hide all polygons with population < 1000"

Master the WHERE clause and you've got 95% of GIS SQL.

The SQL you actually need¶

SELECT *
FROM cities
WHERE state = 'GA'
  AND population > 50000
  AND name LIKE 'A%'
ORDER BY population DESC;

Even ArcGIS Pro's Select by Attributes uses just the WHERE part:

state = 'GA' AND population > 50000 AND name LIKE 'A%'

Operators cheat sheet¶

→ Each one has a dedicated page in SQL for GIS.

ArcGIS Pro SQL dialects¶

ArcGIS Pro uses different SQL syntax depending on the data source:

The differences are small — quoting field names, date literals, and TOP vs LIMIT.

→ Full reference: Esri SQL reference

Spatial SQL (PostGIS)¶

Beyond attribute SQL, spatial SQL lets you do geoprocessing in the database:

-- All schools within 500 m of a fire station
SELECT s.name
FROM schools s
JOIN fire_stations f
  ON ST_DWithin(s.geom, f.geom, 500);

PostGIS, Oracle Spatial, and SQL Server all support spatial SQL. PostGIS is the open-source standard and worth learning.

SQL vs Python¶

In practice, you'll use both. SQL inside Python (gdf.query("pop > 1000")) is extremely common.

Practice¶

Next up¶

→ Remote Sensing Basics — work with satellite imagery.