Grouping database results based on intersection using MySQL GIS?

Grouping Database Results Based on Intersection Using MySQL GIS: A Human’s Guide

So, you’re diving into the world of spatial data with MySQL, huh? Excellent choice! Since way back in version 4.1, MySQL has packed some seriously cool spatial extensions. Think of them as tools that let you store, create, and play around with maps and geographic features right inside your database. And the best part? They play nice with the Open Geospatial Consortium (OGC) standards, so you know you’re getting a solid, reliable toolkit.

One of the trickiest, yet most rewarding, things you can do is group your data based on where things overlap – their intersection. It’s like figuring out which houses fall within a specific school district, or which customers are in a particular sales region. Let’s break down how to make this happen using MySQL’s GIS superpowers.

First things first, let’s get cozy with how MySQL thinks about spatial stuff. It’s all about special data types that represent shapes and spaces. Imagine these as your building blocks:

• GEOMETRY: The “catch-all.” It can hold any kind of geometric shape.
• POINT: Just a single dot on the map. Simple, but powerful.
• LINESTRING: Connect the dots, and you’ve got a line! Think roads, rivers, etc.
• POLYGON: Now close that line, and you’ve got an area. Like a park or a city boundary.
• MULTIPOINT, MULTILINESTRING, MULTIPOLYGON: When one just isn’t enough, use these to group multiple points, lines, or polygons together.

These data types let you bring the real world into your database. Each shape also has a Spatial Reference System Identifier (SRID) attached, which tells MySQL what coordinate system you’re using. Think latitude and longitude, or some other way of pinpointing location.

Okay, shapes are cool, but how do we see if they overlap? That’s where MySQL’s spatial functions come in. And for figuring out intersections, ST_Intersects() is your new best friend.

• ST_Intersects(g1, g2): This function is super straightforward: Does shape g1 touch shape g2? If yes, it spits out a “1”. If no, you get a “0”. From MySQL 5.6.1 onwards, it actually looks at the real shapes to see if they intersect, which is pretty important for accuracy.

Alright, enough theory. Let’s get our hands dirty with an example. Imagine you have two tables: pointtable, which holds a bunch of points (think customer locations), and polygontable, which holds polygons (think sales territories). The goal? Figure out which points fall within each territory.

Here’s the SQL magic to make it happen:

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