How to refer to another table in a CASE WHEN Statement in PostGIS?

Level Up Your Spatial Queries: Referencing Other Tables in a PostGIS CASE WHEN Statement (Human Edition)

PostGIS, that spatial superpower you can bolt onto PostgreSQL, lets you do some seriously cool geospatial analysis right inside your database. And if you really want to crank up the awesome, you gotta master the CASE WHEN statement. Think of it as your “if-then-else” logic for spatial data. But here’s the kicker: what if you need to pull in info from other tables to make those decisions? That’s where things get interesting, and where your queries go from good to “whoa!”. Let’s break down how to reference other tables inside a CASE WHEN statement in PostGIS, and trust me, it’s easier than it sounds.

CASE WHEN: Your Spatial Swiss Army Knife

Okay, quick refresher. The CASE WHEN statement is basically a way to say, “If this is true, then do that; otherwise, do something else.” It’s how you add conditional logic to your SQL. The structure looks a little like this:

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