All fields have properties, which are set when you create a table or feature class. In ArcGIS, the first properties you set for a field are its name and data type. The other properties you set are dependent upon the data type of the field.
Some field properties can be changed after the table or feature class is created. For enterprise geodatabases, the properties that can be changed and how they can be changed depends on the database management system you are using; you can only make changes that your database allows. For example, if your database does not allow you to change the length of a field in a table that contains data, you cannot change the field length through ArcGIS.
Field properties that can be altered are as follows:
- Field Name
Certain system fields cannot be renamed. See Defining feature class properties for a list of these fields.
- Data Type
If the field contains data, you cannot change data types that would lead to loss of data. For example, you cannot change a long integer or float to a short integer, or change a blob to a text.
- Allow or disallow NULL values
If the table or feature class is registered as versioned and its adds table contains data, you cannot change the Allow NULL values property from Yes to No.
- Default Value
If your table or feature class does not contain data, you can increase or decrease this value.
Field properties are accessed from Fields button on the Data contextual tab. Read more about modifying field properties in fields view.