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, 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. If your table or feature class contains data, you can only increase the field length.
Field properties are accessed from the Fields tab of the Table Properties or Feature Class Properties dialog box.
Follow these steps to modify existing field properties:
Start ArcMap or ArcCatalog and connect to the geodatabase that contains the table or feature class for which you want to modify field properties.
If the table or feature class is in an enterprise, workgroup, or desktop geodatabase, you must connect as the table owner to modify field properties.
- Right-click the table or feature class and click Properties.
- Click the Fields tab.
- Choose the field you want to modify from the Field Name list.
- To rename the field, click the text of the name and type a new name.
- To change the data type, choose a new type from the corresponding Data Type drop-down list.
- To change the alias, default value, or length of a field, double-click the value in the Field Properties list and type a new value.
- To change the null value or associated domain for a field, choose a new value from the drop-down list.
- When you finish making all the modifications you needed, click OK to close the Table Properties or Feature Class Properties dialog box and apply your changes.