Oracle 中的OOP概念对象类型,可变数组,嵌套表,对象表,对象视图
对象类型: 优点:1) 更轻易与Java, C++编写的对象应用程序交互2) 获取便捷。一次对象类型请求就可以从多个关系表中获取信息,通过一次网络往复即可返回 语法:CREATE [OR REPLACE] TYPE type_name{{AS IS } OBJECT UNDER super_type}{ attribute_name datatype[,attribute_name datatype]… ---成员变量 [{MAP ORDER} MEMBER function_name,] ---排序函数 [{FINAL NOT FINAL} MEMBER function_name,] ---可否继续的成员函数 [{INSTANTIABLE NOT INSTANTIABLE } MEMBER function_name,] ---可否实例化的成员函数 [{MEMBER STATIC } function_name,] ---静态、非静态成员函数}[{FINAL NOT FINAL}] ---对象可否继续[{INSTANTIABLE NOT INSTANTIABLE }] ---对象可否实例化/ 对象类型的主体部分(即函数的实现部分,可选的):CREATE [OR REPLACE] TYPE BODY type_name {AS IS } [{MAP ORDER} MEMBER function_body,] ---排序函数 [{MEMBER STATIC } function_name,] ---静态、非静态成员函数END;/
例如:create or replace type person as object( first_name varchar2(100), last_name varchar2(100))/ 属性类型可以是任何oracle 数据类型(包括自定义),除了如下:LONG和LONG RAWNCHAR、NCLOB 、NVARCHAR2ROWID、UROWIDPL/SQL的特定类型:%TYPE %ROWTYPE 查看:Desc person 构造函数:set serveroutput on declare l_person personbegin l_person := person(‘Donny’,’Chen’); dbms_output.putline(l_person.first_name);end;/ 构造函数要接受对象类型的所有属性作为参数。因为这些参数没有默认值,即使是null,也要提供。举例: 表中的对象类型:对象类型可以作为数据库中的列,所以称为列对象create table person_table( name person, age number)/ set desc depth alldesc person_table
set desc depth 1 插入数据:insert into person_table values(person(‘Donny’,’Chen’),30); declare l_person personbegin l_person := person(‘Hua’,’Li’); insert into person_table values(l_person,33);end;/ 查询数据:select * from person_table访问对象类型的各个属性:select p.name.first_name from person_table p/ 为避免名称解析问题,要求查询对象类型的属性的时候,使用表别名。否则报错,举例: 对象中的对象(合成):create or replacetype employee as object( name person, empno number, hiredate date)/ 修改和删除对象:9i之前,当建立的对象类型,以及依靠于此类型的对象或表之后,就无法再修改此对象类型了(增加删除属性和成员函数)。唯一的办法是撤销所有以来,即删除依靠于此类型的对象或表。 9i新特性,可以修改被以来的对象类型,成为类型演化。有两种方法:INVALIDATE 和 CASCADE INVALIDATE比如:desc person_table改变person类型,增加新属性ssnalter type person add attribute ssn varchar2(11) INVALIDATE;
desc person (bug可能需要新开一个session) INVALIDATE选项使的所有依靠于person类型的对象和表标记为INVALID,比如:Desc person_table 需要手工验证person_table:alter table person_table upgrade including data;desc person_tableupgrade including data表示根据新类型,物理上更新现有的数据的结构,ssn 置为null。也可以upgrade not including data,不更新原有数据的结构。Dml访问person实例数据的时候再更新。Select * from person_table CASCADE比如:alter type personadd attribute dob datecascade not including table data/ 不用手工验证依靠此对象类型的表,由数据库自动验证。 Desc personDesc person_table 因为not including table data,没有更新原有数据:select * from person_table 删除类型:force 方法:即对象中的过程和函数,3种类型:STATIC: 只能够在对象类型上调用,不专属于某个实例。MEMBER: 专属于某个特定的实例CONSTRUCTOR: 构造函数
create or replacetype employee as object( name person, empno number, hiredate date, sal number, commission number, member function total_compensation return number, static function new(p_empno number, p_person person) return employee)/ desc employee 在类型主体实现这两个方法:create or replacetype body employee as member function total_compensation return number is begin return nvl(self.sal,0) + nvl(self.commission, 0); end; static function new(p_empno number, p_person person) return employee is begin return employee(p_person,p_empno,sysdate,10000,null); end;end;/
比较抽象数据类型的数据:declare l_employee1 employee; l_employee2 employee;begin l_employee1 :=employee.new(12345,null); l_employee2 :=employee.new(67890,null); if l_employee1= l_employee2 then dbms_output.line_put(“They are equal”); end if;end;/ 使用map指定具体比较哪些属性:create or replacetype employee as object( name person, empno number, hiredate date, sal number, commission number, map member function convert return number)/ create or replacetype body employee as map member function convert return number is begin return self.empno; end;end;/
再比较:declare l_employee1 employee; l_employee2 employee;begin l_employee1 :=employee.new(12345,null); l_employee2 :=employee.new(67890,null); if l_employee1= l_employee2 then dbms_output.line_put(“They are equal”); end if; if l_employee1> l_employee2 then dbms_output.line_put(“employee1 is greater”); end if; if l_employee1< l_employee2 then dbms_output.line_put(“employee2 is greater”); end if;end;/ Order 方法:create or replacetype employee as object( name person, empno number, hiredate date, sal number, commission number, order member function match(p_employee employee) return integer)/
create or replacetype body employee as order member function match(p_employee employee) return integer is begin if self.empno> p_employee.empno then return 1; elseif self.empno< p_employee.empno then return -1; else return 0; end if; end;end;/继续:FINAL / NOT FINAL对象默认FINAL,表示不可以被继续;MEMBER方法也能指定是否FINAL,表示能否在子类中对他进行覆写。默认NOT FINAL Create or replace type super_type as object( N number, Final member procedure cannot_override)not final/ 更多内容请看Oracle 10g基础应用 Oracle基础专题,或