Oracle操作XML各种场景介绍

近期在研究Oracle PLSQL中对于XML的系列操作。结合工作中使用的知识和參考资料整理出以下相关内容：

一怎样生成XML文件：

1、使用dbms_xmlquery和utl_file内置包（scott用户运行）

CREATE OR REPLACE DIRECTORY xml_dir AS 'd:\app\xml';

DROP SEQUENCE seq_filename;

CREATE SEQUENCE seq_filename

    MINVALUE 10000

    MAXVALUE 99999

    INCREMENT BY 1

    START WITH 10000

    NOCYCLE;

DECLARE

    v_filename  Varchar2(50)  := 'Empmsg'||to_char(seq_filename.nextval)||'.xml';

    xml_str     clob;

    xml_file    utl_file.file_type;

    offset      number;

    buffer      varchar2(32767);

    buffer_size number;

BEGIN

    offset      := 1;

    buffer_size := 3000;

    xml_file := utl_file.fopen('XML_DIR', v_filename, 'w');

    xml_str  := dbms_xmlquery.getxml('select empno,

                                             ename,

                                             job,

                                             mgr,

                                             hiredate,

                                             sal,

                                             comm,

                                             deptno

                                      from emp');

    while (offset < dbms_lob.getlength(xml_str)) loop

      buffer := dbms_lob.substr(xml_str, buffer_size, offset);

      utl_file.put(xml_file, buffer);

      utl_file.fflush(xml_file);

      offset := offset + buffer_size;

    end loop;

    utl_file.fclose(xml_file);

END;

2、使用XMLELEMENT系列内置函数返回xml（sys用户运行）

DECLARE

    v_filename  Varchar2(50)  := 'Empmsg'||to_char(scott.seq_filename.nextval)||'.xml';

    xml_str     clob;

    xml_file    utl_file.file_type;

    offset      number;

    buffer      varchar2(32767);

    buffer_size number;

BEGIN

    offset      := 1;

    buffer_size := 3000;

    xml_file := utl_file.fopen('XML_DIR', v_filename, 'w');

    SELECT XMLElement("DEPARTMENT"

                 , XMLAttributes( department_id as "ID"

                                , department_name as "NAME"

                                )

                 , XMLElement("EMPLOYEES"

                             , (SELECT XMLAgg( XMLElement("EMPLOYEE"

                                                         , XMLForest(employee_id as "ID"

                                                                    ,first_name||' '||last_name as "NAME"

                                                                    )

                                                         )

                                             )

                                 FROM hr.employees emp

                                WHERE emp.department_id = dept.department_id

                                )

                              )

                ).getclobval() INTO xml_str

     FROM hr.departments dept

     WHERE department_id = 20;

    while (offset < dbms_lob.getlength(xml_str)) loop

      buffer := dbms_lob.substr(xml_str, buffer_size, offset);

      utl_file.put(xml_file, buffer);

      utl_file.fflush(xml_file);

      offset := offset + buffer_size;

    end loop;

    utl_file.fclose(xml_file);

END;

--XMLElement: 将一个关系值转换为XML元素的函数。格式为<elementName>值</elementName>
--XMLAttributes: 用于在SQL查询返回的 XML 元素中设置属性的函数
--XMLForest: 该函数返回一个或多个子元素的集合,该函数使用列名做为XML元素的名称并用SQL值表达式做为XML元素的内容。但使用时不能指定元素的属性
--XMLAgg: 在GROUP BY查询中对XML数据进行分组或汇总的函数

PS: 使用SPOOL方式导出文件：

SET TRIMSPOOL ON

SET TERMOUT ON

SET FEEDBACK OFF

SET VERIFY OFF

SET ECHO OFF

SET PAGESIZE 999

SET HEAD OFF

SET HEADING OFF

SET LONG 5000

spool c:\a.xml

SELECT XMLElement("DEPARTMENT"

                 , XMLAttributes( department_id as "ID"

                                , department_name as "NAME"

                                )

                 , XMLElement("EMPLOYEES"

                             , (SELECT XMLAgg( XMLElement("EMPLOYEE"

                                                         , XMLForest(employee_id as "ID"

                                                                    ,first_name||' '||last_name as "NAME"

                                                                    )

                                                         )

                                             )

                                 FROM employees emp

                                WHERE emp.department_id = dept.department_id

                                )

                              )

                ) a

  FROM departments dept

 WHERE department_id = 10;

spool off

二怎样存储XML文件内容：

我们知道oracle 中xmltype数据类型用来存储XML内容。

以下样例中介绍怎样将系统中XML文件内容载入至

含有XMLTYPE类型的表中。

CREATE TABLE xml_table OF XMLTYPE;

INSERT INTO xml_table

    VALUES(XMLTYPE(bfilename('XML_DIR','PurchaseOrder.xml'),nls_charset_id('AL32UTF8')));

    SELECT x.sys_nc_rowinfo$.getstringval() FROM xml_table x;

CREATE TABLE table_with_xml_column(filename VARCHAR2(64), xml_document XMLTYPE);

INSERT INTO table_with_xml_column

    VALUES ('PurchaseOrder.xml',XMLType(bfilename('XML_DIR', 'PurchaseOrder.xml'),nls_charset_id('AL32UTF8')));

SELECT x.xml_document.getCLOBVal() FROM table_with_xml_column x;

PurchaseOrder.xml内容：

<PurchaseOrder xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  xsi:noNamespaceSchemaLocation=

    "http://localhost:8080/source/schemas/poSource/xsd/purchaseOrder.xsd">

  <Reference>SBELL-2002100912333601PDT</Reference>

  <Actions>

    <Action>

      <User>SVOLLMAN</User>

    </Action>

  </Actions>

  <Reject/>

  <Requestor>Sarah J. Bell</Requestor>

  <User>SBELL</User>

  <CostCenter>S30</CostCenter>

  <ShippingInstructions>

    <name>Sarah J. Bell</name>

    <address>400 Oracle Parkway

      Redwood Shores

      CA

      94065

      USA</address>

    <telephone>650 506 7400</telephone>

  </ShippingInstructions>

  <SpecialInstructions>Air Mail</SpecialInstructions>

  <LineItems>

    <LineItem ItemNumber="1">

      <Description>A Night to Remember</Description>

      <Part Id="715515009058" UnitPrice="39.95" Quantity="2"/>

    </LineItem>

    <LineItem ItemNumber="2">

      <Description>The Unbearable Lightness Of Being</Description>

      <Part Id="37429140222" UnitPrice="29.95" Quantity="2"/>

    </LineItem>

    <LineItem ItemNumber="3">

      <Description>Sisters</Description>

      <Part Id="715515011020" UnitPrice="29.95" Quantity="4"/>

    </LineItem>

  </LineItems>

</PurchaseOrder>

三怎样解析XML内容：

1、XPath结构介绍：

/ 表示树根。

比如：/PO 指向树根的子节点<PO>; 通常也作为路径分隔符使用，比如：/A/B

//
表示当前节点下全部子节点；比如：/A//B 匹配A节点下全部B节点

* 作为通配符使用，匹配全部子节点；如：/A/*/C 匹配A节点下全部子节点C

[ ] 表示预期表达式；XPath支持丰富的操作符如OR、AND、NOT等；比如：/PO[PONO=20 AND PNAME="PO_2"]/SHIPADDR 匹配全部订单号为20而且订单名为PO_2的送货地址

@ 用来提取节点属性

FunctionsXPath支持一些内置函数如：substring(), round() 和 not().

2、使用XMLTYPE方法查询XML：

SELECT x.OBJECT_VALUE.getCLOBVal() FROM xml_table x;

SELECT x.OBJECT_VALUE.getSTRINGVal() FROM xml_table x;

3、使用函数解析XML：

--existsNode 推断XPath中节点是否存在，存在返回值1 不存在返回0；

SELECT existsNode(OBJECT_VALUE, '/PurchaseOrder/Reference')

FROM purchaseorder;

--extractValue 提取XPath节点值

SELECT extractValue(OBJECT_VALUE, '/PurchaseOrder/Reference')

FROM purchaseorder

WHERE existsNode(OBJECT_VALUE, '/PurchaseOrder/Reference') = 1;

--extract 提取XPath节点

SELECT extract(OBJECT_VALUE, '/PurchaseOrder/Reference') "REFERENCE"

FROM purchaseorder;

4、使用SQL解析XML：

SELECT extractValue(OBJECT_VALUE, '/PurchaseOrder/Reference') REFERENCE,

    extractValue(OBJECT_VALUE, '/PurchaseOrder/*//User') USERID,

    CASE

        WHEN existsNode(OBJECT_VALUE, '/PurchaseOrder/Reject') = 1

        THEN 'Rejected'

        ELSE 'Accepted'

    END "STATUS",

extractValue(OBJECT_VALUE, '//CostCenter') CostCenter

FROM purchaseorder

WHERE existsNode(OBJECT_VALUE,'//Reject') = 1;

四 XMLTABLE使用方法：

XMLTable maps the result of an XQuery evaluation into
relational rows and columns. You can query the result returned by the function as a virtual relational table using SQL.

说白了就是解析XML内容返回虚拟关系型结构数据。以下说个简单样例：

CREATE TABLE warehouses(

	warehouse_id NUMBER(3),

	warehouse_spec SYS.XMLTYPE,

	warehouse_name VARCHAR2(35),

location_id NUMBER(4)

);

INSERT into warehouses (warehouse_id, warehouse_spec,warehouse_name) VALUES (100, sys.XMLType.createXML(

'<Warehouse whNo="100">

   <opt1>

        <Building>Owned</Building>

        <WaterAccess>WaterAccess</WaterAccess>

        <RailAccess>RailAccess</RailAccess>

        <field>f1</field>

        <field>f2</field>

        <field>f3</field>

   </opt1>

   <opt2>

        <name>Dylan</name>

   </opt2>

</Warehouse>'),'Warehouse-X');

SELECT warehouse_name warehouse,

   warehouse2."whNo"

FROM warehouses,

   XMLTABLE('/Warehouse'

      PASSING warehouses.warehouse_spec

      COLUMNS

         "whNo" varchar2(100) PATH '@whNo')

      warehouse2;

SELECT warehouse_name warehouse,

   warehouse2."Water", warehouse2."Rail", warehouse2.field

   FROM warehouses,

   XMLTABLE('*//opt1'

      PASSING warehouses.warehouse_spec

      COLUMNS

         "Water" varchar2(100) PATH '//WaterAccess',

         "Rail" varchar2(100) PATH '//RailAccess',

         field XMLTYPE PATH '/')

      warehouse2;

具体文章链接： http://viralpatel.net/blogs/oracle-xmltable-tutorial/

to be continue...

----------------------------------

By Dylan.