QGIS 2.0 Table Join creates unwanted prefix in field names

QGIS Table Joins: Ditching That Annoying Prefix

Ever tried merging data in QGIS, only to find your attribute table looking like a jumbled mess of prefixed field names? Yeah, it’s a common headache. You’re trying to bring together information from different sources, which is super useful, but suddenly all your field names have this extra bit tacked on – usually the source file’s name. It can get pretty annoying, especially when you’re dealing with tons of fields or files with ridiculously long names!

So, why does QGIS do this? Well, it’s all about preventing those dreaded naming conflicts. Imagine joining two tables, both with a field called “ID.” QGIS needs a way to tell them apart, so it automatically adds a prefix. Makes sense in theory, but in practice, it can feel like overkill, especially when you just want clean, simple field names.

And here’s where it gets even trickier: shapefiles. Remember those? Good old .shp files have a strict 10-character limit for field names. So, if your prefix plus the original field name goes over that limit, QGIS chops it off! Suddenly, “Land_Use_Type” becomes “Land_Use_T,” which isn’t exactly helpful. I’ve definitely been there, staring blankly at truncated field names, wondering what on earth they’re supposed to mean.

But don’t worry, there are ways to wrangle this prefix problem. Here are a few tricks I’ve picked up over the years:

A few extra tips to keep in mind:

• Plan Ahead: Before you start joining, take a moment to think about your field names. Are there any potential conflicts? Can you rename anything beforehand to make things smoother? A little planning goes a long way.
• Unique IDs are Your Friends: Whenever possible, use unique identifiers like FIPS codes as your join fields. They’re much less likely to cause naming conflicts than something generic like “City Name.”
• Make it Permanent: Remember, a table join in QGIS is initially just a virtual thing. To make it stick, you need to save the joined layer as a new file.

Dealing with those unwanted prefixes in QGIS table joins can be a bit of a pain, but with these tips and tricks, you can keep your attribute tables clean, organized, and (most importantly) understandable. Happy mapping!