SQL语句PART5

Confirming granted privileges
Data Dictionary View                Description
ROLE_SYS_PRIVS                System privileges granted to roles
ROLE_TAB_PRIVS                Table privileges granted to roles
USER_ROLE_PRIVS             Roles accessible by the user
USER_SYS_PRIVS               System privileges granted to the user
USER_TAB_PRIVS_MADE     Object privileges granted on the user's objects
USER_TAB_PRIVS_RECD     Object privileges granted to the user
USER_ROLE_PRIVS_MADE  Object privileges granted on the columns of the user's objects
USER_ROLE_PRIVS_RECD:  Object privileges granted to the user on specific columns
Revoking Object Privileges
grammer:
revoke {privileges [, privileges...] | all}
on object from {user [,...user...] | role | pubic} cascade constraints;
// privileges granted to others through the WITH GRANT OPTION clause are also revoked.
 Alter table statement
grammer:
alter table table1 add (column datatype [default expr] [, column datatype]...);
alter table table1 modify (column datatype [default expr] [, column datatype]...);
alter table table1 drop (column);
Alter table (set unused option)
grammer:
alter table <table_name> set unsed (<column_name>);
or
alter table <table_name> set unsed column <column_name>;
then:
alter table <table_name> drop unused columns;
Constraint: Adding a constraint Syntax
grammer:
alter table <table_name> add [constraint <constraint_name>] type (<column_name>);
e.g.:
alter table emp2 modify employee_id primary key;
alter table emp2 add constraint emp_mgr_fk foreign key(manager_id) references emp2(employee_id);