Oracle XML 表解析不获取没有子节点的节点答案

【问题标题】：Oracle XML Table Parsing not fetching the nodes without childOracle XML 表解析不获取没有子节点的节点
【发布时间】：2018-06-24 10:35:07
【问题描述】：

我正在运行下面的 sql 来解析 XML，但只有当子节点存在时，它才会返回我的父节点。

     select
       nvxml.catalogs,nvlvl.levels L1,nvlvl.L1_CAT_ID,lvl2.l2 , lvl2.L2_CAT_ID 
       --, nvlvl.L1_CAT_ID ,lvl2.L2, lvl2.l2_cat_id
     from
      XMLTABLE('//category'  PASSING XMLTYPE.CREATEXML (


      '<categories>
      <category  name="Business Services">
       <L1  name="Mail, Messenger and Delivery" categoryID="BSSRVMMDSV" /> 
       <L1  name="Office Supplies" categoryID="BSSRVOFFSP" /> 
       <L1  name="Translation & Interpretation" categoryID="BSSRVLNGSP" /> 
       </category>

     <category  name="Telecommunications">
      <L1  name="Mobile and Service Plans" categoryID="TLCOMHHWDB">
       <L2  name="Mobile - Upgrade" categoryID="WHHDDBBDU" /> 
       <L2  name="New Mobile and Plans" categoryID="PDAS_TMBB8820OWHHDDNBBDP" /> 
       <L2  name="Mobile - Repair" categoryID="WHHDDBBDR" /> 
       <L2  name="Mobile Access to Notes" categoryID="WHHDDBBNACC" /> 
       <L2  name="Mobile Plan - Change" categoryID="WHHDDBBPC" /> 
       <L2  name="Mobile Service - Cancel" categoryID="WHHDDBBSC" /> 
       </L1>
     </category>
     </categories>'



      )
          COLUMNS catalogs VARCHAR2(300)   PATH  '@name' , 
                  levels   XMLTYPE        PATH  '//L1' ,
                  levels2   XMLTYPE        PATH  '//L1//L2') nvxml ,

     XMLTABLE('//L1'  passing nvxml.levels
          columns   
        --  levels2   XMLTYPE        PATH  '//L2' ,
          levels varchar2(300) PATH '@name',
          L1_CAT_ID VARCHAR2(300) PATH '@categoryID' ) nvlvl ,

     XMLTABLE ('//L2'  passing nvxml.levels2
          columns   
          L2 varchar2(300) PATH '@name',
          L2_CAT_ID VARCHAR2(300) PATH '@categoryID') lvl2

我应该怎么做才能获得没有子 L2 的 L1 值？

【问题讨论】：

标签： oracle xml-parsing relation xmltable

【解决方案1】：

为此，您需要将查询转换为使用 ANSI 连接语法，以便您可以对 lvl2 xmltable 执行 LEFT OUTER JOIN，如下所示：

SELECT nvxml.catalogs,
       nvlvl.levels l1,
       nvlvl.l1_cat_id,
       lvl2.l2,
       lvl2.l2_cat_id
--, nvlvl.L1_CAT_ID ,lvl2.L2, lvl2.l2_cat_id
FROM   xmltable('//category' passing XMLTYPE('<categories>
      <category  name="Business Services">
       <L1  name="Mail, Messenger and Delivery" categoryID="BSSRVMMDSV" /> 
       <L1  name="Office Supplies" categoryID="BSSRVOFFSP" /> 
       <L1  name="Translation &amp; Interpretation" categoryID="BSSRVLNGSP" /> 
       </category>

     <category  name="Telecommunications">
      <L1  name="Mobile and Service Plans" categoryID="TLCOMHHWDB">
       <L2  name="Mobile - Upgrade" categoryID="WHHDDBBDU" /> 
       <L2  name="New Mobile and Plans" categoryID="PDAS_TMBB8820OWHHDDNBBDP" /> 
       <L2  name="Mobile - Repair" categoryID="WHHDDBBDR" /> 
       <L2  name="Mobile Access to Notes" categoryID="WHHDDBBNACC" /> 
       <L2  name="Mobile Plan - Change" categoryID="WHHDDBBPC" /> 
       <L2  name="Mobile Service - Cancel" categoryID="WHHDDBBSC" /> 
       </L1>
     </category>
     </categories>')
      columns catalogs VARCHAR2(300) path '@name',
              levels xmltype path '//L1',
              levels2 xmltype path '//L1//L2') nvxml
       CROSS JOIN
       xmltable('//L1' passing nvxml.levels columns
                --  levels2   XMLTYPE        PATH  '//L2' ,
                levels VARCHAR2(300) path '@name',
                l1_cat_id VARCHAR2(300) path '@categoryID') nvlvl
       LEFT OUTER JOIN xmltable('//L2' passing nvxml.levels2 columns l2 VARCHAR2(300) path '@name', l2_cat_id VARCHAR2(300) path '@categoryID') lvl2 ON 1=1;

CATALOGS             L1                                       L1_CAT_ID    L2                        L2_CAT_ID
-------------------- ---------------------------------------- ------------ ------------------------- ----------------------------
Business Services    Mail, Messenger and Delivery             BSSRVMMDSV                             
Business Services    Office Supplies                          BSSRVOFFSP                             
Business Services    Translation & Interpretation             BSSRVLNGSP                             
Telecommunications   Mobile and Service Plans                 TLCOMHHWDB   Mobile - Upgrade          WHHDDBBDU
Telecommunications   Mobile and Service Plans                 TLCOMHHWDB   New Mobile and Plans      PDAS_TMBB8820OWHHDDNBBDP
Telecommunications   Mobile and Service Plans                 TLCOMHHWDB   Mobile - Repair           WHHDDBBDR
Telecommunications   Mobile and Service Plans                 TLCOMHHWDB   Mobile Access to Notes    WHHDDBBNACC
Telecommunications   Mobile and Service Plans                 TLCOMHHWDB   Mobile Plan - Change      WHHDDBBPC
Telecommunications   Mobile and Service Plans                 TLCOMHHWDB   Mobile Service - Cancel   WHHDDBBSC

【讨论】：