Primary key or index cannot be created on column <Columnname> because its data type is <Datatypename>. (Visual Database Tools)
You have included in an index or primary key a column whose data type precludes its participation in keys or indexes. Change the column's data type or remove it from the index or primary key.
For the rules restricting the data types of index and key columns, see Creating Indexes (Database Engine).
See Also
Concepts
Error Messages in Visual Database Tools