Unique identifier fields

All layers in ArcGIS—including query layers, layers from geodatabases, and layers from databases—require a unique identifier.

To use a field as a unique identifier in ArcGIS desktop apps, the field must be not null, must contain unique values, and be one of the following data types:

  • String
  • GUID
  • Date

Values in the field must always be unique and not null. It is your responsibility to guarantee that values in this field meet these requirements.


You will receive an error if ArcGIS encounters a null value, but ArcGIS does not enforce the uniqueness of values in the unique identifier field used in a query layer or database table. If ArcGIS encounters a nonunique value, no error is returned; however, you may see inconsistent results in selection sets or other queries in ArcGIS.

To publish the query layer in a feature layer (a feature service) that references the registered data store, the ID must be a single, not null, unique, autoincrementing, 32-bit, integer field.