Fundamentals of adding and deleting fields

You can add or remove fields from a table or feature class. Most likely, you'll add or remove fields from data that you personally manage.

You can add or remove fields as long as the following conditions are met:

• You have write access to the data.
• You're not currently editing the data in ArcMap.
• No other users or applications are accessing the data including other ArcMap or ArcCatalog sessions.

Large organizations typically have databases with well-defined schemas that outline the contents, including fields, of the database. Unless you manage the database, it is unlikely that you'll be able to add or remove fields.

To add a new field, you need to specify the field's data type and any required properties. For example, you need to specify length for string fields and precision and scale for numeric fields in ArcSDE geodatabases.

The Add Field dialog box only lists the field types and properties supported by the particular data source to which you're adding the field. For example, you won't see the BLOB field type in the Add Field dialog box unless you are working with a geodatabase. In addition, if you are adding a numeric field to a personal or file geodatabase, you won't see the precision and scale properties since they only apply to ArcSDE geodatabases.

Follow these links to learn more about fields and working with them in various data sources:

• Defining fields in geodatabase tables
• Geodatabase field data types
• Coverages
• Shapefiles or dBASE tables

Field naming guidelines

Field names need to adhere to certain conventions for them to be valid. Keep the following guidelines in mind when you name a field:

• Spaces and certain characters are not supported in field names. Special characters include hyphens such as in x-coordinate and y-coordinate; parentheses; brackets; and symbols such as $, %, and #. Essentially, eliminate anything that is not alphanumeric or an underscore.
• Be sure to edit the field names in delimited text files or other tables to remove unsupported characters before trying to use the files in ArcGIS.
• Avoid starting field names with a number or an underscore.
• Avoid using field names that contain words that are considered reserved keywords, such as date, day, month, table, text, user, when, where, year, and zone. Each underlying DBMS can have its own set of reserved keywords. For a list of keywords for MS Access, see this Microsoft support article.
• Geodatabase feature class, table, and field names can be up to 64 characters. (More specifically, you can only enter up to 52 characters for a personal geodatabase feature class name because the system appends characters to total 64.) Shapefiles and .dbf field names can be up to 10 characters long. For INFO tables, use up to 16 letters or numbers. In addition, the underlying DBMS may impose other restrictions on field names.

Note:

Remember that you can set a field alias if you need special characters, spaces, additional length, and so on. Aliases do not have to adhere to the limitations of the database, so you can give names to fields that are more descriptive than their actual field name. For example, you might specify an alias of Date of deed for a field stored in the geodatabase as DEED_DATE.