怎么理解数据库集合元素的删除

这篇文章主要介绍"怎么理解数据库集合元素的删除"，在日常操作中，相信很多人在怎么理解数据库集合元素的删除问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"怎么理解数据库集合元素的删除"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

我创建了一个嵌套表类型和过程：

CREATE OR REPLACE TYPE plch_numbers_t IS TABLE OF NUMBER;/CREATE OR REPLACE PROCEDURE plch_show_numbers (   title_in     IN VARCHAR2, numbers_in   IN plch_numbers_t)ISBEGIN   DBMS_OUTPUT.put_line (title_in);   FOR rec IN (SELECT COLUMN_VALUE FROM TABLE (numbers_in))   LOOP      DBMS_OUTPUT.put_line (rec.COLUMN_VALUE);   END LOOP;END;/

下面的选项用来代替下列代码块的 /*BODY*/ 注释:

DECLARE   l_numbers   plch_numbers_t       := plch_numbers_t (12, 23, 34, 45, 56                        , 67, 78, 89, 90, 100);BEGIN   /*BODY*/   plch_show_numbers ('AFTER DELETE', l_numbers);END;/

哪些选项使得这个块执行之后会显示如下文本：

AFTER DELETE23456789

换而言之，所有偶数元素都被删除了。

(A)

FOR indx IN 1 .. l_numbers.COUNTLOOP   IF MOD (indx, 2) = 0   THEN      l_numbers.delete (indx);   END IF;END LOOP;

SQL> DECLARE  2    l_numbers plch_numbers_t := plch_numbers_t(12,  3                                               23,  4                                               34,  5                                               45,  6                                               56,  7                                               67,  8                                               78,  9                                               89, 10                                               90, 11                                               100); 12  BEGIN 13    FOR indx IN 1 .. l_numbers.COUNT LOOP 14      IF MOD(indx, 2) = 0 THEN 15        l_numbers.delete(indx); 16      END IF; 17    END LOOP; 18   19    plch_show_numbers('AFTER DELETE', l_numbers); 20  END; 21  /AFTER DELETE1234567890PL/SQL procedure successfully completedSQL>

(B)

FOR indx IN 1 .. l_numbers.COUNTLOOP   IF MOD (l_numbers (indx), 2) = 0   THEN      l_numbers.delete (indx);   END IF;END LOOP;

SQL> DECLARE  2    l_numbers plch_numbers_t := plch_numbers_t(12,  3                                               23,  4                                               34,  5                                               45,  6                                               56,  7                                               67,  8                                               78,  9                                               89, 10                                               90, 11                                               100); 12  BEGIN 13    FOR indx IN 1 .. l_numbers.COUNT LOOP 14      IF MOD(l_numbers(indx), 2) = 0 THEN 15        l_numbers.delete(indx); 16      END IF; 17    END LOOP; 18   19    plch_show_numbers('AFTER DELETE', l_numbers); 20  END; 21  /AFTER DELETE23456789PL/SQL procedure successfully completedSQL>

(C)

DELETE FROM TABLE (l_numbers)      WHERE MOD (index_value, 2) = 0;

SQL> DECLARE  2    l_numbers plch_numbers_t := plch_numbers_t(12,  3                                               23,  4                                               34,  5                                               45,  6                                               56,  7                                               67,  8                                               78,  9                                               89, 10                                               90, 11                                               100); 12  BEGIN 13    DELETE FROM TABLE(l_numbers) WHERE MOD(index_value, 2) = 0; 14   15    plch_show_numbers('AFTER DELETE', l_numbers); 16  END; 17  /DECLARE  l_numbers plch_numbers_t := plch_numbers_t(12,                                             23,                                             34,                                             45,                                             56,                                             67,                                             78,                                             89,                                             90,                                             100);BEGIN  DELETE FROM TABLE(l_numbers) WHERE MOD(index_value, 2) = 0;  plch_show_numbers('AFTER DELETE', l_numbers);END;ORA-06550: 第 13 行, 第 15 列: PL/SQL: ORA-00903: 表名无效ORA-06550: 第 13 行, 第 3 列: PL/SQL: SQL Statement ignoredSQL>

(D)

FOR rec IN (SELECT *              FROM TABLE (l_numbers)             WHERE MOD (COLUMN_VALUE, 2) = 0)LOOP   l_numbers.delete (rec.COLUMN_VALUE);END LOOP;

SQL> DECLARE  2    l_numbers plch_numbers_t := plch_numbers_t(12,  3                                               23,  4                                               34,  5                                               45,  6                                               56,  7                                               67,  8                                               78,  9                                               89, 10                                               90, 11                                               100); 12  BEGIN 13    FOR rec IN (SELECT * FROM TABLE(l_numbers) WHERE MOD(COLUMN_VALUE, 2) = 0) LOOP 14      l_numbers.delete(rec.COLUMN_VALUE); 15    END LOOP; 16   17    plch_show_numbers('AFTER DELETE', l_numbers); 18  END; 19  /AFTER DELETE122334455667788990100PL/SQL procedure successfully completedSQL>

实测答案为B

到此，关于"怎么理解数据库集合元素的删除"的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注网站，小编会继续努力为大家带来更多实用的文章！