16.2.1 System permissions
1. The revocation of system permissions will not be cascaded (this is different from the revocation of object permissions)
2. If the user revokes the authority, any operation performed by the user with the corresponding authority (such as creating a table) will be intact. In addition, if the user is granted permission with the admin option, then even if it is revoked, any user he granted permission will retain the permission. Do not save the record of the system authority grantor, so there is no revocation cascade
3. Grammar: grant privilege [, privilege ...] to username;
grant privilege [,privilege...] to username with admin option;
16.2.2 Object permissions
1. Any permission is for each object permission in each user account in the database, it is a system permission, not an object permission;
2. Object permissions apply to different types of objects, as follows:
| Authority | Authorized object |
| select | Tables, views, sequences and synonyms |
| insert | Tables, views, and synonyms |
| update | Tables, views, and synonyms |
| delete | Tables, views, and synonyms |
| alter | Tables, views and sequences |
| execute | Procedures, functions, packages and synonyms |
3.语法：grant privilege on schema.object to username [with grant option];
4. The revocation of object permissions will be cascaded (this is different from the revocation of system permissions)
supplement:
1. View all tables in hr mode
> select table_name from dba_tables where owner = 'HR'; a kind of query
>conn hr/hr@pdboaec;
> select table_name from user_tables; another way