Oracle TYPE OBJECT详解

2023年9月6日 732次阅读来源: SQL

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最近在自学PL/SQL高级编程，了解到对象类型（OBJECT TYPE）。

特意搜索了一下10G官方文档，下面不才基于此进行拓展：

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1. 介绍

Object-oriented programming is especially suited for building reusable components and complex

applications.

尤其适合于构建可重用的部件和复杂的应用程序的面向对象的编程。

In PL/SQL, object-oriented programming is based on object types.

在PL / SQL，面向对象的程序设计是基于对象类型。

They let you model real-world objects, separate interfaces and implementation details, and store
object-oriented data persistently in the database.
他们坚持让你模拟现实世界的对象，单独的接口和实现细节，面向对象的数据和存储在数据库中。

2. PL / SQL的声明和初始化对象

对象的类型可以代表任何真实世界的实体。例如，一个对象的类型可以代表一个学生，银行帐户，电脑屏幕上

，合理数量，或数据结构，如队列，堆栈，或列表。

CREATE OR REPLACE TYPE address_typ AS OBJECT (
       street          VARCHAR2(30),                     
       city            VARCHAR2(20),
       state           CHAR(2),                            
       postal_code     VARCHAR2(6)  
        );

CREATE OR REPLACE TYPE employee_typ AS OBJECT(
       employee_id       NUMBER(6),
       first_name        VARCHAR2(20),
       last_name         VARCHAR2(25),
       email             VARCHAR2(25),
       phone_number      VARCHAR2(25),
       hire_date         DATE,
       job_id            VARCHAR2(25),                                                   
       salary            NUMBER(8,2),              
       commission_pct    NUMBER(2,2),                                                   
       manager_id        NUMBER(6),                                                   
       department_id     NUMBER(4),                                                   
       address           address_typ                                                   
       MAP MEMBER FUNCTION get_idno RETURN NUMBER,                                                   
       MEMBER PROCEDURE display_address(SELF IN OUT NOCOPY employee_typ)
       );

—
创建对象体

CREATE TYPE BODY employee_typ AS
  MAP MEMBER FUNCTION get_idno RETURN NUMBER IS
  BEGIN
    RETURN employee_id;
  END;
  MEMBER PROCEDURE display_address ( SELF IN OUT NOCOPY employee_typ ) IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE(first_name || ' '  || last_name);
    DBMS_OUTPUT.PUT_LINE(address.street);
    DBMS_OUTPUT.PUT_LINE(address.city || ', '  || address.state || ' ' ||
                         address.postal_code);   
  END;
END;

—
持久化对象

CREATE TABLE employee_tab OF employee_typ;
CREATE TYPE  emp_typ as table of employee_typ;

3. 在PL/SQL块中声明对象：

DECLARE
  emp employee_typ; -- emp is atomically null
BEGIN
-- call the constructor for employee_typ
  emp := employee_typ(315, 'Francis', 'Logan', 'FLOGAN',
        '555.777.2222', to_date('2012-12-24', 'yyyy-mm-dd'), 'SA_MAN', 11000, .15, 101, 110,
         address_typ('376 Mission', 'San Francisco', 'CA', '94222'));
  DBMS_OUTPUT.PUT_LINE(emp.first_name || ' ' || emp.last_name); -- display details
  emp.display_address();  -- call object method to display details
END;

4. PL/SQL如何处理未初始化的对象：

DECLARE
  emp employee_typ; -- emp is atomically null
BEGIN
  IF emp IS NULL THEN DBMS_OUTPUT.PUT_LINE('emp is NULL #1'); END IF;
  IF emp.employee_id IS NULL THEN
     DBMS_OUTPUT.PUT_LINE('emp.employee_id is NULL #1');
  END IF;
  emp.employee_id := 330;
  IF emp IS NULL THEN DBMS_OUTPUT.PUT_LINE('emp is NULL #2'); END IF;
  IF emp.employee_id IS NULL THEN
    DBMS_OUTPUT.PUT_LINE('emp.employee_id is NULL #2');
  END IF;
  emp := employee_typ(NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL,
         address_typ(NULL, NULL, NULL, NULL));
  -- emp := NULL; -- this would have made the following IF statement TRUE
  IF emp IS NULL THEN DBMS_OUTPUT.PUT_LINE('emp is NULL #3'); END IF;
  IF emp.employee_id IS NULL THEN
    DBMS_OUTPUT.PUT_LINE('emp.employee_id is NULL #3');
  END IF;
EXCEPTION
   WHEN ACCESS_INTO_NULL THEN
     DBMS_OUTPUT.PUT_LINE('Cannot assign value to NULL object');
END;

5. 在PL/SQL中操纵对象：

5.1.调用对象构造器和方法（Calling Object Constructors and Methods）

DECLARE
  emp employee_typ;
BEGIN
  INSERT INTO employee_tab VALUES (employee_typ(310, 'Evers', 'Boston', 'EBOSTON',
   '555.111.2222', to_date('2012-12-24', 'yyyy-mm-dd'), 'SA_REP', 9000, .15, 101, 110,
    address_typ('123 Main', 'San Francisco', 'CA', '94111')) );
  INSERT INTO employee_tab VALUES (employee_typ(320, 'Martha', 'Dunn', 'MDUNN',
    '555.111.3333', to_date('2012-11-5', 'yyyy-mm-dd'), 'AC_MGR', 12500, 0, 101, 110,
    address_typ('123 Broadway', 'Redwood City', 'CA', '94065')) );
END;

5.2 更新和删除对象：

DECLARE
  emp employee_typ;
BEGIN
  INSERT INTO employee_tab VALUES (employee_typ(370, 'Robert', 'Myers', 'RMYERS',
   '555.111.2277', to_date('2012-3-7', 'yyyy-mm-dd'), 'SA_REP', 8800, .12, 101, 110,
    address_typ('540 Fillmore', 'San Francisco', 'CA', '94011')) );
  UPDATE employee_tab e SET e.address.street = '1040 California'
     WHERE e.employee_id = 370;
  DELETE FROM employee_tab e WHERE e.employee_id = 310;
END;

6. 通过REF修饰符操纵对象：

DECLARE
  emp           employee_typ;
  emp_ref   REF employee_typ;
  emp_name      VARCHAR2(50);
BEGIN
  SELECT REF(e) INTO emp_ref FROM employee_tab e WHERE e.employee_id = 370;
-- the following assignment raises an error, not allowed in PL/SQL
-- emp_name := emp_ref.first_name || ' ' || emp_ref.last_name;
-- emp := DEREF(emp_ref); not allowed, cannot use DEREF in procedural statements
  SELECT DEREF(emp_ref) INTO emp FROM DUAL; -- use dummy table DUAL
  emp_name := emp.first_name || ' ' || emp.last_name;
  DBMS_OUTPUT.PUT_LINE(emp_name);
END;

7. 定义相当于PL/SQL集合类型的SQL类型（Defining SQL Types Equivalent to PL/SQL Collection Types）

7.1 定义嵌套表：

—
建嵌套表类型

CREATE TYPE CourseList AS TABLE OF VARCHAR2(10) — define type

—
建对象类型

CREATE TYPE student AS OBJECT ( — create object

id_num INTEGER(4),

name VARCHAR2(25),

address VARCHAR2(35),

status CHAR(2),

courses CourseList); — declare nested table as attribute

–建立嵌套表类型表

CREATE TABLE sophomores of student

NESTED TABLE courses STORE AS courses_nt;

–插入数据

insert into sophomores

values(1,’dylan’,’CARL STREET’,’ACTIVE’,

CourseList(‘MATH1020’)

);

–查询

SELECT a.*, b.*

from sophomores a, TABLE(a.courses) b;

select /*+ nested_table_get_refs */ *

from courses_nt t;

7.2 定义数组：

—
声明数组类型（Each project has a 16-character code name）

— We will store up to 50 projects at a time in a database column.

CREATE TYPE ProjectList AS VARRAY(50) OF VARCHAR2(16);

–
-创建表

CREATE TABLE dept_projects ( — create database table

dept_id NUMBER(2),

name VARCHAR2(15),

budget NUMBER(11,2),

— Each department can have up to 50 projects.

projects ProjectList);

–插入数据：

INSERT INTO dept_projects

VALUES(60, ‘Security’, 750400,

ProjectList(‘New Badges’, ‘Track Computers’, ‘Check Exits’));

8. 在动态SQL中使用对象：

8.1 定义对象类型person_typ和数组类型hobbies_var,并创建报TEAMS:

CREATE TYPE person_typ AS OBJECT (name VARCHAR2(25), age NUMBER);

CREATE TYPE hobbies_var AS VARRAY(10) OF VARCHAR2(25);

CREATE OR REPLACE PACKAGE teams
   AUTHID CURRENT_USER AS
   PROCEDURE create_table (tab_name VARCHAR2);
   PROCEDURE insert_row (tab_name VARCHAR2, p person_typ, h hobbies_var);
   PROCEDURE print_table (tab_name VARCHAR2);
END;

CREATE OR REPLACE PACKAGE BODY teams AS
   PROCEDURE create_table (tab_name VARCHAR2) IS
   BEGIN
      EXECUTE IMMEDIATE 'CREATE TABLE ' || tab_name ||
                        ' (pers person_typ, hobbs hobbies_var)';
   END;
   PROCEDURE insert_row (
      tab_name VARCHAR2,
      p person_typ,
      h hobbies_var) IS
   BEGIN
      EXECUTE IMMEDIATE 'INSERT INTO ' || tab_name ||
         ' VALUES (:1, :2)' USING p, h;
   END;
   PROCEDURE print_table (tab_name VARCHAR2) IS
      TYPE  refcurtyp IS REF CURSOR;
      v_cur refcurtyp;
      p     person_typ;
      h     hobbies_var;
   BEGIN
      OPEN v_cur FOR 'SELECT pers, hobbs FROM ' || tab_name;
      LOOP
         FETCH v_cur INTO p, h;
         EXIT WHEN v_cur%NOTFOUND;
         -- print attributes of 'p' and elements of 'h'
         DBMS_OUTPUT.PUT_LINE('Name: ' || p.name || ' - Age: ' || p.age);
         FOR i IN h.FIRST..h.LAST
         LOOP
           DBMS_OUTPUT.PUT_LINE('Hobby(' || i || '): ' || h(i));
         END LOOP;
      END LOOP;
      CLOSE v_cur;
   END;
END;

8.2 调用TEAMS包中的存储过程：

DECLARE
   team_name VARCHAR2(15);
BEGIN
   team_name := 'Notables';
   TEAMS.create_table(team_name);
   TEAMS.insert_row(team_name, person_typ('John', 31),
      hobbies_var('skiing', 'coin collecting', 'tennis'));
   TEAMS.insert_row(team_name, person_typ('Mary', 28),
      hobbies_var('golf', 'quilting', 'rock climbing', 'fencing'));
   TEAMS.print_table(team_name);
END;

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output:

Name: John – Age: 31

Hobby(1): skiing

Hobby(2): coin collecting

Hobby(3): tennis

Name: Mary – Age: 28

Hobby(1): golf

Hobby(2): quilting

Hobby(3): rock climbing

Hobby(4): fencing

PL/SQL 过程已成功完成。

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    原文作者：SQL
    原文地址: https://blog.csdn.net/IndexMan/article/details/8435426
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