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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) IS BEGIN 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 DELETE 23 45 67 89
换而言之,所有偶数元素都被删除了。
(A)
FOR indx IN 1 .. l_numbers.COUNT LOOP 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 DELETE 12 34 56 78 90 PL/SQL procedure successfully completed SQL>
(B)
FOR indx IN 1 .. l_numbers.COUNT LOOP 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 DELETE 23 45 67 89 PL/SQL procedure successfully completed SQL>
(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 ignored SQL>
(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 DELETE 12 23 34 45 56 67 78 89 90 100 PL/SQL procedure successfully completed SQL>
实测答案为B
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