In a database table, each field must have a unique name. That name cannot include spaces or special characters, though underscores are allowed. The allowed length of the field name will depend on the type of database. Is it adBase,Access, orSQL Servertable? Each of these has its own limitations.
As a rule of thumb, I have learned that keeping my field names limited to 7 to 8 characters works best. This will prevent field names from getting shortened if you export the data to a different format that does not support the name length of your native database.
This often happens when your GIS data is stored as a geodatabase that supports long field names, but you export to a shapefile that does not. Shapefiles store attributes in a dBase format that does not support long field names. Being an older database type, dBase only supports field names of 7 to 8 characters. So, a field that is named as parcel_indentification_number in your geodatabase may get renamed...