怎么理解数据库的定义者权限与使用者权限

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我在HR模式下运行了下列语句（没有发生错误）:

CREATE TABLE plch_parts(   partnum    NUMBER, partname   VARCHAR2 (50))/BEGIN   INSERT INTO plch_parts        VALUES (123, 'Steering Wheel');   INSERT INTO plch_parts        VALUES (456, 'Brake Pedal');   COMMIT;END;/CREATE OR REPLACE TYPE plch_numbers_t IS TABLE OF NUMBER/CREATE OR REPLACE FUNCTION plch_func   RETURN plch_numbers_t   AUTHID CURRENT_USERIS   l_numbers   plch_numbers_t;BEGIN   SELECT partnum     BULK COLLECT INTO l_numbers     FROM plch_parts;   RETURN l_numbers;END;/CREATE OR REPLACE VIEW plch_func_vAS   SELECT COLUMN_VALUE partnum FROM TABLE (plch_func ())/GRANT SELECT ON plch_func_v TO scott/GRANT EXECUTE ON plch_func TO scott/

然后我又连接到SCOTT模式并执行如下语句：

CREATE TABLE plch_parts(   partnum    NUMBER, partname   VARCHAR2 (50))/BEGIN   INSERT INTO plch_parts        VALUES (100, 'Tire');   INSERT INTO plch_parts        VALUES (101, 'Battery');   COMMIT;END;/

哪些选项显示了下列语句块执行后屏幕上的输出结果？

BEGIN   DBMS_OUTPUT.put_line ('Two Cursor For Loops....');   FOR rec IN (  SELECT p.partname                   FROM TABLE (hr.plch_func) v, plch_parts p                  WHERE v.column_value = p.partnum               ORDER BY p.partnum)   LOOP      DBMS_OUTPUT.put_line (rec.partname);   END LOOP;   FOR rec IN (  SELECT p.partname                   FROM hr.plch_func_v v, plch_parts p                  WHERE v.partnum = p.partnum               ORDER BY p.partnum)   LOOP      DBMS_OUTPUT.put_line (rec.partname);   END LOOP;END;/

(A)

Two Cursor For Loops....Steering WheelBrake Pedal

(B)

An unhandled exception:PLS-00158: AUTHID CURRENT_USER subprograms not allowed in views

(C)

Two Cursor For Loops....TireBattery

(D)

Two Cursor For Loops....TireBatterySteering WheelBrake Pedal

(E)

Two Cursor For Loops....TireBatteryTireBattery

实测答案C

SQL> BEGIN  2     DBMS_OUTPUT.put_line ('Two Cursor For Loops....');  3    4     FOR rec IN (  SELECT p.partname  5                     FROM TABLE (yoga.plch_func) v, plch_parts p  6                    WHERE v.column_value = p.partnum  7                 ORDER BY p.partnum)  8     LOOP  9        DBMS_OUTPUT.put_line (rec.partname); 10     END LOOP; 11   12     FOR rec IN (  SELECT p.partname 13                     FROM yoga.plch_func_v v, plch_parts p 14                    WHERE v.partnum = p.partnum 15                 ORDER BY p.partnum) 16     LOOP 17        DBMS_OUTPUT.put_line (rec.partname); 18     END LOOP; 19  END; 20  /Two Cursor For Loops....TireBatteryPL/SQL procedure successfully completedSQL>

答案C.

一个定义为调用者权限（AUTHID CURRENT_USER）的函数，如果它在一个VIEW或者触发器中被调用，这时是按照定义者的权限来运作的，所以你通过VIEW看到的将是OWNER的数据，而不是当前用户的数据。

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