Changing Field Types
Change a field type by opening a field and selecting another field type from the drop-down list box. However, this feature is intended as a design-time change—that is, before your tables are created in the database. While you can convert some field types, the results vary depending on your database platform.
Note:
If you change a field from one type to another, you must rebuild all records containing that field by running the Alter process. Use Find Definition References to find all instances of the changed field.
See Altering Tables.