对象类型:
优点:
1) 更容易与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,] ---可否继承的成员函数
[{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
}
对象类型
优点:
1) 更容易与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,] ---可否继承的成员函数
[{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}] ---对象可否继承
[{INSTANTIABLE | NOT INSTANTIABLE }] ---对象可否实例化
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
例如:
create or replace
type person as object(
first_name varchar2(100),
last_name varchar2(100))
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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 RAW
NCHAR、NCLOB 、NVARCHAR2
ROWID、UROWID
PL/SQL的特定类型:%TYPE %ROWTYPE
查看:
Desc person
构造函数:
set serveroutput on
declare
l_person person
begin
l_person := person(‘Donny’,’Chen’);
dbms_output.putline(l_person.first_name);
end;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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 all
desc person_table
set desc depth 1
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
插入数据:
insert into person_table
values(person(‘Donny’,’Chen’),30);
declare
l_person person
begin
l_person := person(‘Hua’,’Li’);
insert into person_table values(l_person,33);
end;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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 replace
type 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,以及依赖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,即删除依赖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ssn
alter type person
add attribute ssn varchar2(11) INVALIDATE;
desc person (bug可能需要新开一个session)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
INVALIDATE选项使的所有依赖于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_table
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
upgrade 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 person
add attribute dob date
cascade not including table data
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
不用手工验证依赖此对象类型的表,由数据库自动验证。
Desc person
Desc 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 replace
type 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 replace
type 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;
/
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
使用map指定具体比较哪些属性:
create or replace
type employee as object(
name person,
empno number,
hiredate date,
sal number,
commission number,
map member function convert return number)
/
create or replace
type body employee as
map member function convert return number is
begin
return self.empno;
end;
end;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
Order 方法:
create or replace
type employee as object(
name person,
empno number,
hiredate date,
sal number,
commission number,
order member function match(p_employee employee) return integer)
/
create or replace
type 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;
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
继承:
FINAL / NOT FINAL
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
对象默认FINAL,表示不可以被继承;
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
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)