怎么求数据库嵌套表平均值

这篇文章主要介绍"怎么求数据库嵌套表平均值"，在日常操作中，相信很多人在怎么求数据库嵌套表平均值问题上存在疑惑，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"怎么求数据库嵌套表平均值"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SCHEMA级别的NUMBER型嵌套表：

CREATE OR REPLACE TYPE plch_numbers_t IS TABLE OF NUMBER/

哪些选项实现了一个名字为plch_avg的函数，能够计算一个上述嵌套表中所有元素的平均值，从而使得下列代码块执行之后会显示"3.5"?

DECLARE   l_numbers   plch_numbers_t                  := plch_numbers_t (1, 2, 3, 4, 5, 6);BEGIN   DBMS_OUTPUT.put_line (plch_avg (l_numbers));END;/

(A)

CREATE OR REPLACE FUNCTION plch_avg (numbers_in IN plch_numbers_t)   RETURN NUMBERIS   l_index   PLS_INTEGER := numbers_in.FIRST;   l_sum     NUMBER := 0;BEGIN   WHILE l_index IS NOT NULL   LOOP      l_sum := l_sum + numbers_in (l_index);      l_index := numbers_in.NEXT (l_index);   END LOOP;   RETURN l_sum / numbers_in.COUNT;END;/

(B)

CREATE OR REPLACE FUNCTION plch_avg (numbers_in IN plch_numbers_t)   RETURN NUMBERIS   l_average   NUMBER;BEGIN   SELECT AVG (COLUMN_VALUE) INTO l_average     FROM TABLE (numbers_in);   RETURN l_average;END;/

(C)

CREATE OR REPLACE FUNCTION plch_avg (numbers_in IN plch_numbers_t)   RETURN NUMBERISBEGIN   RETURN AVG (numbers_in);END;/

(D)

CREATE OR REPLACE FUNCTION plch_avg (numbers_in IN plch_numbers_t)   RETURN NUMBERIS   l_index   PLS_INTEGER := numbers_in.FIRST;   l_average     NUMBER := 0;BEGIN   WHILE l_index IS NOT NULL   LOOP      l_average := l_average + numbers_in (l_index)/numbers_in.count;      l_index := numbers_in.NEXT (l_index);   END LOOP;   RETURN l_average;END;/

(E)

CREATE OR REPLACE FUNCTION plch_avg (numbers_in IN plch_numbers_t)   RETURN NUMBERIS   l_average   NUMBER;BEGIN   SELECT AVG (numbers_in(ROWNUM)) INTO l_average     FROM numbers_in;   RETURN l_average;END;/

实测答案ABC

C报错 PLS-00204: 函数或伪列 'AVG' 只能在 SQL 语句中使用

E报错 PL/SQL: ORA-00942: 表或视图不存在

答案ABD, B是最佳答案，注意D在某些情况下可能出现误差。

到此，关于"怎么求数据库嵌套表平均值"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！