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 注释:
DECLARE
l_numbers plch_numbers_t
:= plch_numbers_t (12, 23, 34, 45, 56
, 67, 78, 89, 90, 100);
BEGIN
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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