sometimes during database migration, we need To know if our database have NVARCHAR Field , below SQL can check Oracle database if it have NVARCHAR field.
select table_name,column_name,data_type from user_tab_columns where data_type like 'NVARCHAR%';
select owner, table_name,column_name,data_type from dba_tab_columns where data_type like 'NVARCHAR%';