When you create a table or add a field to a table in the geodatabase, fields are created as a specific data type. Data types are classifications that identify possible values for and operations that can be done on the data, as well as the way the data in that field is stored in the database.
When you import data of one type into a field of another data type, you need to understand what the equivalent data types are between ArcGIS and your database management system (DBMS), because it can impact data content.
Data type mapping
ArcGIS works with specific data types. If you store your data in a database or a geodatabase in a database, ArcGIS data types and the data types of the database management system (DBMS) may not match directly. When you import data of one type into a field of another data type, you need to understand what the equivalent data types are between ArcGIS and your database management system (DBMS), because it can impact data content.
Data type mapping is the process of matching data types to the closest database data type available. In this process, it is possible that the values will be stored in the database as a different type, applying different criteria to the data attribute. As a result, the data type you see in the table or feature class properties in ArcGIS AllSource may change from what you initially defined.
For example, if you add a floating-point (float) column to an existing feature class, it equates to a numeric data type column in a Microsoft SQL Server database.
Note:
Moving data from one database to another can cause data types to remap.
File and mobile geodatabase data types are the same as ArcGIS data types. For DBMS products, though, data types can differ. To learn more about how ArcGIS data types map to DBMS data types, see DBMS data types supported in ArcGIS.
Other data storage formats, such as shapefiles or dBase file (DBF) tables, have different data type limitations. Be sure you know the data type and size limitations of your destination storage format when moving data between data storage types.