GDB vs MDB vs SHP
If you’re a bit confused whether or not to use a file geodatabase (*.gdb) or personal geodatabase (*.mdb)…
Or maybe you just want to know what a geodatabase is.
Then we’re here to set things straight.
Here’s everything you need to know about personal and file geodatabases.
Why geodatabases stand out in spatial data storage…
Geodatabases are an organized way to keep similar data together. Anything that is relevant stays in a single database.
For example, a city might have their wastewater division, land records, transportation and fire departments connected and using different geodatabases.
Compared to plain ol’ shapefiles, full-blown geodatabases deliver extra capabilities. Geodatabases allows you to set up a topology, which you can’t do with shapefiles.
When you can add coded value domains, raster catalogs, relationship classes and geometric networks, geodatabases truly are the multi-functional engine an organization needs.
Geodatabases also excel in performance. Spatial functions run quicker in a database such as Performance Querying Indexing.
Because shapefiles use DBFs as a table structure, fields are limited to only 13 characters. Geodatabases offer more in field names and you get more geoprocessing performance.
Why file geodatabases are so incredibly good
Once upon a time, the geodatabase format of choice was the Microsoft Access database format (MDB). However, the downside to this format was its harsh 2 GB size limitation.
Now, for a typical Microsoft Access user this limit was fine. But the growing file sizes in raster and vector data sunk the hearts of countless GIS users filling the database to the brim.
To correct this issue, Esri developed their own proprietary file geodatabase. In windows explorer, they consist of binary files stored in a system folder. But the key to the file geodatabase was that there really was no size limit to this type of database.
File geodatabases allow users to compress them, create spatial indexes to quickly locate features, manage raster data with tiles and edit data more efficiently with multiple users.
Despite the fact that file geodatabases are proprietary and sometimes fragile, file geodatabases reign supreme for datasets massive in size.
Don’t count the personal geodatabase out yet…
Personal geodatabases have some limitations to functionality and size. Based on the Microsoft Access (MDB) database format, it has a 2 GB size limit.
Despite the size restrictions of Access databases, it opens the possibility for ODBC access from external applications as a database back-end. For example, ODBC can grab and manipulate attribute data from a personal geodatabase into a statistical software application like R.
It also has some querying capabilities that allows users to take advantage of the full underlying RDBMS. Users can query data with keywords such as “DISTINCT” or “ORDER BY” with a personal geodatabase.
Personal geodatabases are a great choice for outputs and analysis. But most of the time, file geodatabase is the optimal choice because of its compression, spatial indexes, raster tiles and editing capabilities.
But sometimes shapefiles are the answer too…
Shapefiles contain a number of files all working cohesively together. At the very least, you’ll have shp, shx and dbf which really give you the geometry, attribute information and indexing.
Shapefiles truly are the most portable format in GIS today. As it has become a standard in storage of GIS data, almost 100% of GIS software packages can consume it.
Even if you have a dozen files all over the place for your shapefiles, at least others can read it if they use different GIS software. Because once a geodatabase (especially file geodatabase) is outside an Esri environment, it suddenly becomes less consumable.
Within an Esri environment, file geodatabases reign supreme. If sharing outside, then shapefile can be accessed in practically any GIS software.
READ MORE: ArcGIS Shapefile Files Types & Extensions
The Final Word
When geodatabases were first introduced, it was like a lollapalooza in the GIS community. It changed how organizations stored, editing and published their data.
The shift from static shapefiles to geodatabases has opened up a world to relational database management and data integrity.
There is a time and place to use personal geodatabases and file geodatabases depending on the situation…
But the shapefile still finds its place for cross-platform sharing.