하......
I created tables without errors, but this happened when I tried to create view.
https://www.databasestar.com/ora-01031/
This link have all kinds of permission error in sql.
So I searched about "grant", and this link helped me.
https://www.ibm.com/docs/en/netcoolomnibus/8.1?topic=reference-grant-command
Thanks to this, I fixed the problem.
Open the CMD, type "sqlplus" -->type user name and pwd-->type "conn sys as sysdba"--> type "grant create any view to [username];"
