Joy for the tables that join

Blog Post created by geonetadmin on Dec 23, 2010
Ah, the holidays. What better time of year for joining together with friends, families…and tables? Hello, this is Cassandra again bringing you the good tidings of tips for making sure your tables join in harmony.

We talk to a many customers who experience odd problems with data that has been joined, such as an attribute table that contains NULL values, empty output or odd errors when performing geoprocessing. The most common reason why these problems occur is because one or more of the field names in the joined table or the name of the joined table itself does not follow the required naming convention rules.

Naming convention rules, as directed by the Microsoft JET engine, which enables Windows applications like ArcMap to read various table formats, include the following:

- The name must start with a letter, not a number.
- The name must not contain spaces.- The only special character allowed is an underscore.

Take a look at this Excel table – how many names do you see that will cause problems?


If you experience problems performing joins or relates or displaying XY data on tables, exporting the resultant joined table or performing subsequent geoprocessing on a joined table, your first step should be to check all the field and table names.

Another trick I’ve learned when your problem is a field name but you don’t see any problems, is to save the table as a CSV format file and then try to add that CSV into ArcMap. If there is a problem with any field name, ArcMap will display an error message stating which field is the problem.


So, while I can’t fix Aunt Harriet’s fruitcake or that crazy tie you got in the Holiday secret Santa exchange, take comfort that you know your tables join.

Happy holidays from all of us at Esri Support Services!