--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;

查詢oracl用戶信息