Oracle UpdateXML（）更改XML結構？

Question

當我打電話給UpdateXML()時，我發現空節點正在轉換爲速記XML。有沒有辦法阻止UpdateXML()以這種方式運行，也許是一個標誌或設置或替代XPath表達式來告訴它保留原始結構？

/* Example 1 */ 
SELECT UpdateXML(xmlData, '/TEST/VALUE/text()', 'hello') as "Example 1" 
    FROM (SELECT XMLType('<TEST><VALUE>hi</VALUE></TEST>') as xmlData 
      FROM DUAL); 

Example 1 
--------- 
<TEST><VALUE>hello</VALUE></TEST> 


/* Example 2 */ 
SELECT UpdateXML(xmlData, '/TEST/VALUE/text()', 'hello') as "Example 2" 
    FROM (SELECT XMLType('<TEST><VALUE></VALUE></TEST>') as xmlData 
      FROM DUAL); 

Example 2 
--------- 
<TEST><VALUE/></TEST> 

我想看到什麼：

/* Desired Output, vs. Example 2 */ 
SELECT UpdateXML(xmlData, '/TEST/VALUE/text()', 'hello') as "Desired Output" 
    FROM (SELECT XMLType('<TEST><VALUE></VALUE></TEST>') as xmlData 
      FROM DUAL); 

Desired Output 
-------------- 
<TEST><VALUE></VALUE></TEST> 

Answer 1

我想你可以用臨時值替換空的文本，更新所有其他的文本，然後用替換臨時值避免問題一個null。

我不明白的XPath，有可能是一個更好的方法來做到這一點，但是這似乎工作：

SELECT 
    --#3: Replace the temporary value with null, this keeps the start and end tag 
    UpdateXML(
     --#2: Replace everything but the temporary value 
     UpdateXML(
      --#1: Replace empty text with a temporary value 
      UpdateXML(xmlData, '/TEST/VALUE[not(text())]', '<VALUE>TEMPORARY VALUE</VALUE>') 
     ,'/TEST/VALUE[text()!="TEMPORARY VALUE"]/text()', 'hello') 
    ,'/TEST/VALUE[text()="TEMPORARY VALUE"]/text()', null) examle 
FROM (SELECT XMLType('<TEST><VALUE>hi</VALUE><VALUE>hola</VALUE><VALUE></VALUE></TEST>') as xmlData FROM DUAL);