在执行存储过程时，我们可能会遇到权限问题

● 定义者权限存储过程
● 调用者权限存储过程

在数据库中创建存储过程时，定义者权限是缺省模式
当指定AUTHID CURRENT_USER关键字后，便是调用者权限存储过程
他俩之间最根本的差异在于role能否在存储过程中生效

㈠ 定义者权限存储过程问题
定义者权限存储过程role无效，必须要有显式授权
即便是拥有dba role，还是不能访问不同用户的表

sys@EMREP> grant connect,resource to u1 identified by u1;

Grant succeeded.
sys@EMREP> grant dba to u2 identified by u2;

Grant succeeded.
sys@EMREP> conn u1/u1
Connected.
u1@EMREP> create table t as select * from user_objects;

Table created.
sys@EMREP> conn u2/u2
Connected.
u2@EMREP> create or replace procedure p_test
  2  as
  3  begin
  4    delete from u1.t;
  5    commit;
  6  end;
  7  /

Warning: Procedure created with compilation errors.

u2@EMREP> show error;
Errors for PROCEDURE P_TEST:

LINE/COL ERROR
-------- -----------------------------------------------------------------
4/3      PL/SQL: SQL Statement ignored
4/18     PL/SQL: ORA-00942: table or view does not exist

u2@EMREP> conn u1/u1
Connected.
u1@EMREP> grant all on t to u2;

Grant succeeded.

u1@EMREP> conn u2/u2
Connected.
u2@EMREP> create or replace procedure p_test
  2  as
  3  begin
  4    delete from u1.t;
  5    commit;
  6  end;
  7  /

Procedure created.

㈡ 调用者权限存储过程问题
调用者权限存储过程role编译不可见，但运行时可见
用动态SQL避免直接授权，而将权限的检查延后至运行时

u2@EMREP> conn u1/u1           
Connected.
u1@EMREP> revoke all on t from u2;

Revoke succeeded.

u1@EMREP> conn u2/u2
Connected.
u2@EMREP> create or replace procedure p_test
  2  authid current_user
  3  as
  4  begin
  5    delete from u1.t;
  6    commit;
  7  end;
  8  /

Warning: Procedure created with compilation errors.

u2@EMREP> show error;
Errors for PROCEDURE P_TEST:

LINE/COL ERROR
-------- -----------------------------------------------------------------
5/3      PL/SQL: SQL Statement ignored
5/18     PL/SQL: ORA-00942: table or view does not exist
u2@EMREP> create or replace procedure p_test
  2  authid current_user
  3  as
  4  begin
  5    execute immediate
  6   'delete from u1.t';
  7    commit;
  8  end;
  9  /

Procedure created.

u2@EMREP> exec p_test;

PL/SQL procedure successfully completed.

u2@EMREP> select count(*) from u1.t;

  COUNT(*)
----------
         0