ITPub博客

首页 > 数据库 > Oracle > oracle存储过程中的数组

oracle存储过程中的数组

原创 Oracle 作者:wangzh3 时间:2006-05-05 18:25:34 0 删除 编辑

之前遇到过一个老兄,问我是否会写存储过程,我自问也写过数百个存储过程,也对不少过程进行优化,尽管没有什么系统的理论知识,就回答说,比较熟,这老兄就问我有没有用过数组,说实话,用过,但是不太记得了,用的比较少,不是很熟,这个老兄说:写存储过程如果没有用过数组,就和没写过存储过程差不多。

虽然不赞同这老兄的说法,不过还是觉得应该研究一下的。这个老兄的意思是说,你可以把结果集放在一个结构数组中,这样子在内存里面访问起来比较快。我觉得应该是一样子的,因为都是在内存里面,即使是游标,因为存储过程都是在oracle的SGA里面的。

下面是一段网上的说明,觉得虽然例子看起来复杂了点但是还是很清晰的说明了数组的应用。

[@more@]

type index_table is table of varchar2(2000) index by binary_integer;
type nested_table is table of varchar2(2000);
type v_arrary is varray(1000) of varchar2(2000);
---------------------------------------------------------------

A PL/SQL table is a single column array. The PL/SQL table is indexed by a binary integer counter so you can reference any value stored in a PL/SQL table in an indexed fashion. The number of rows in a PL/SQL table is dynamic, it can be increased as desired.

PL/SQL tables are declared in two steps. First, the table type is declared, then the PL/SQL table variable is assigned to that table type.

The PL/SQL declarations can occur in any block of a pl/sql construct. A PL/SQL table cannot be initialized in its declaration. The first reference to a PL/SQL table must be an assignment statement or a NO_DATA_FOUND will result. PL/SQL tables follow the same scope rules as other variables and cease to exist when the package, function or procedure is exited.


Example:

In this example, we declare a table type of NUMBER and then assign two tables, results and n10. Notice how the indexes are used in each to specify a specific value.

CREATE OR REPLACE FUNCTION max_value RETURN NUMBER IS
TYPE numtab IS TABLE OF NUMBER
INDEX BY BINARY_INTEGER;
results numtab;
n10 numtab;
max_loop NUMBER;
temp_store NUMBER;
CURSOR get_results IS
SELECT result FROM result_table;
i integer;
x integer:=1;
j integer:=1;
BEGIN
OPEN get_results;
FOR i IN 1..1500 LOOP
FETCH get_results INTO temp_store;
IF i = MOD(x,15) THEN
results(j):=temp_store;
END IF;
END LOOP;
j:=1;
FOR i IN 1..10 LOOP
n10(i):=GREATEST(results(j),results(j+1),results(j+2),
results(j+3),results(j+4),results(j+6),
results(j+7),results(j+7),results(j+8),
results(j+9));
j:=j+10;
END LOOP;
j:=1
max_loop:=GREATEST(n10(j),n10(j+1),n10(j+2),
n10(j+3),n10(j+4),n10(j+5),n10(j+6),n10(j+7),
n10(j+8),n10(j+9);
RETURN max_loop;
END;

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/47869/viewspace-832241/,如需转载,请注明出处,否则将追究法律责任。

上一篇: ipod nano
下一篇: 一声叹息
请登录后发表评论 登录
全部评论
  • 博文量
    301
  • 访问量
    10831595