本篇内容介绍了“怎么判断数据库集合的密集性”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
我创建了这个工具函数来显示一个布尔型变量的值：
CREATE OR REPLACE PROCEDURE plch_bpl (val IN BOOLEAN)
IS
BEGIN
DBMS_OUTPUT.put_line (
CASE val WHEN TRUE THEN 'TRUE' WHEN FALSE THEN 'FALSE' ELSE 'NULL' END);
END plch_bpl;
/下列的选项中都包含了下面这个函数的实现代码：
CREATE OR REPLACE FUNCTION plch_is_dense (numbers_in IN DBMS_SQL.number_table)
RETURN BOOLEAN我写了另一个帮助过程来测试这个 plch_is_dense 函数:
CREATE OR REPLACE PROCEDURE plch_test_is_dense
IS
l_numbers DBMS_SQL.number_table;
BEGIN
l_numbers (1000) := 1;
l_numbers (3000) := 1;
plch_bpl (plch_is_dense (l_numbers));
l_numbers.delete;
l_numbers (2) := 1;
l_numbers (3) := 1;
plch_bpl (plch_is_dense (l_numbers));
END;
/哪些选项创建的plch_is_dense使得plch_test_is_dense在执行之后会显示这两行文本？
FALSE
TRUE(A)
IS
BEGIN
RETURN numbers_in.COUNT = (numbers_in.LAST - numbers_in.FIRST);
END;(B)
IS
l_number NUMBER;
BEGIN
FOR indx IN numbers_in.FIRST .. numbers_in.LAST
LOOP
l_number := numbers_in (indx);
END LOOP;
RETURN TRUE;
EXCEPTION
WHEN NO_DATA_FOUND
THEN
RETURN FALSE;
END;(C)
IS
l_number NUMBER;
BEGIN
FOR indx IN 1 .. numbers_in.COUNT
LOOP
l_number := numbers_in (indx);
END LOOP;
RETURN TRUE;
EXCEPTION
WHEN NO_DATA_FOUND
THEN
RETURN FALSE;
END;(D)
IS
BEGIN
RETURN numbers_in.COUNT = (numbers_in.LAST - numbers_in.FIRST + 1);
END;运行结果如下
(A)
CREATE OR REPLACE FUNCTION plch_is_dense(numbers_in IN DBMS_SQL.number_table)
RETURN BOOLEAN IS
BEGIN
RETURN numbers_in.COUNT =(numbers_in.LAST - numbers_in.FIRST);
END;
/SQL> exec plch_test_is_dense;
FALSE
FALSE
PL/SQL procedure successfully completed
SQL>(B)
CREATE OR REPLACE FUNCTION plch_is_dense(numbers_in IN DBMS_SQL.number_table)
RETURN BOOLEAN IS
l_number NUMBER;
BEGIN
FOR indx IN numbers_in.FIRST .. numbers_in.LAST LOOP
l_number := numbers_in(indx);
END LOOP;
RETURN TRUE;
EXCEPTION
WHEN NO_DATA_FOUND THEN
RETURN FALSE;
END;
/SQL> exec plch_test_is_dense;
FALSE
TRUE
PL/SQL procedure successfully completed
SQL>(C)
CREATE OR REPLACE FUNCTION plch_is_dense(numbers_in IN DBMS_SQL.number_table)
RETURN BOOLEAN IS
l_number NUMBER;
BEGIN
FOR indx IN 1 .. numbers_in.COUNT LOOP
l_number := numbers_in(indx);
END LOOP;
RETURN TRUE;
EXCEPTION
WHEN NO_DATA_FOUND THEN
RETURN FALSE;
END;
/SQL> exec plch_test_is_dense;
FALSE
FALSE
PL/SQL procedure successfully completed
SQL>(D)
CREATE OR REPLACE FUNCTION plch_is_dense(numbers_in IN DBMS_SQL.number_table)
RETURN BOOLEAN IS
BEGIN
RETURN numbers_in.COUNT =(numbers_in.LAST - numbers_in.FIRST + 1);
END;
/SQL> exec plch_test_is_dense;
FALSE
TRUE
PL/SQL procedure successfully completed
SQL>10-31答案BD. 对于非密集型的COLLECTION访问不能从1开始，而是要用FIRST方法。访问不存在的元素会引发NO_DATA_FOUND异常。“怎么判断数据库集合的密集性”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注亿速云网站，小编将为大家输出更多高质量的实用文章！
