1.查看所有用戶：

select * from dba_users; 
select * from all_users; 
select * from user_users;

2.查看用戶或角色系統權限(直接賦值給用戶或角色的系統權限)：

select * from dba_sys_privs; 
select * from user_sys_privs; (查看當前用戶所擁有的權限)

3.查看角色(只能查看登陸用戶擁有的角色)所包含的權限

sql>select * from role_sys_privs;

4.查看用戶對象權限：

select * from dba_tab_privs; 
select * from all_tab_privs; 
select * from user_tab_privs;

5.查看所有角色： select * from dba_roles;

6.查看用戶或角色所擁有的角色：

select * from dba_role_privs; 
select * from user_role_privs;

7.查看哪些用戶有sysdba或sysoper系統權限(查詢時需要相應權限)

select * from V$PWFILE_USERS

8.SqlPlus中查看一個用戶所擁有權限

SQL>select * from dba_sys_privs where grantee=‘username‘; 其中的username即用戶名要大寫才行。
比如： SQL>select * from dba_sys_privs where grantee=‘TOM‘;

9、Oracle刪除指定用戶所有表的方法

select ‘Drop table ‘||table_name||‘;‘ from all_tables where owner=‘要刪除的用戶名(註意要大寫)‘;

10、刪除用戶

drop user user_name cascade; 如：drop user SMCHANNEL CASCADE

11、獲取當前用戶下所有的表：

select table_name from user_tables;

12、刪除某用戶下所有的表數據:

select ‘truncate table ‘ || table_name from user_tables;

13、禁止外鍵 ORACLE數據庫中的外鍵約束名都在表user_constraints中可以查到。

其中constraint_type=‘R‘表示是外鍵約束。

啟用外鍵約束的命令為：alter table table_name enable constraint constraint_name 
禁用外鍵約束的命令為：alter table table_name disable constraint constraint_name

然後再用SQL查出數據庫中所以外鍵的約束名：

select ‘alter table ‘||table_name||‘ enable constraint ‘||constraint_name||‘;‘ from user_constraints where constraint_type=‘R‘select ‘alter table ‘||table_name||‘ disable constraint ‘||constraint_name||‘;‘ from user_constraints where constraint_type=‘R‘

14、ORACLE禁用/啟用外鍵和觸發器 --啟用腳本

SET SERVEROUTPUT ON SIZE 1000000
BEGIN
for c in (select ‘ALTER TABLE ‘||TABLE_NAME||‘ ENABLE CONSTRAINT ‘||constraint_name||‘ ‘ as v_sql from user_constraints
where CONSTRAINT_TYPE=‘R‘) loop
DBMS_OUTPUT.PUT_LINE(C.V_SQL);
begin
EXECUTE IMMEDIATE c.v_sql;
exception when others then
dbms_output.put_line(sqlerrm);
end;
end loop; 
for c in (select ‘ALTER TABLE ‘||TNAME||‘ ENABLE ALL TRIGGERS ‘ AS v_sql from tab where tabtype=‘TABLE‘) loop
dbms_output.put_line(c.v_sql);
begin
execute immediate c.v_sql;
exception when others then
dbms_output.put_line(sqlerrm);
end;
end loop;
end;
/ 
commit;

--禁用腳本

SET SERVEROUTPUT ON SIZE 1000000
BEGIN
for c in (select ‘ALTER TABLE ‘||TABLE_NAME||‘ DISABLE CONSTRAINT ‘||constraint_name||‘ ‘ as v_sql from user_constraints
where CONSTRAINT_TYPE=‘R‘) loop
DBMS_OUTPUT.PUT_LINE(C.V_SQL);
begin
EXECUTE IMMEDIATE c.v_sql;
exception when others then
dbms_output.put_line(sqlerrm);
end;
end loop; 
for c in (select ‘ALTER TABLE ‘||TNAME||‘ DISABLE ALL TRIGGERS ‘ AS v_sql from tab where tabtype=‘TABLE‘) loop
dbms_output.put_line(c.v_sql);
begin
execute immediate c.v_sql;
exception when others then
dbms_output.put_line(sqlerrm);
end;
end loop;
end;
/
commit;

如何查詢Oracle中所有用戶信息