Xquery从XML中获取特定元素的值，该XML在DB2中存储为[XML Nullable column](Xquery to get the value of a specific element from an XML which is stored as [XML Nullable column] in DB2)

 请考虑以下XML： 
 
     <Employee>
        <EmpDetails>   
             <Name>huff</Name>
        </EmpDetails>
     </Employee>
 
 以上[XML NULLABLE]在DB2中的表中以数据类型[XML NULLABLE]形式存储为column(DATA) 。 假设表的结构是这样的： 
 
      Table name:  REGEVENT
     Columns are: REFID (VARCHAR), APPID(VARCHAR), DATA(XML NULLABLE)
 
 假设表中的值是： REFID(12345) ， APPID(54321) ，DATA（如上所述的Employee xml）。 
 
 现在我必须使用Xquery获取存储在DATA列中的XML中的元素值（或者任何其他方式也可以）。 
 
 我正在尝试以下查询，但我得到的值EmpName为NULL。 
 
select XMLCAST(XMLQUERY('$d/Employee/EmpDetails/Name' PASSING rg.DATA AS "d") AS VARCHAR(50)) AS EmpName from REGEVENT  rg where REFID='12345';

Consider the following XML :
 
     <Employee>
        <EmpDetails>   
             <Name>huff</Name>
        </EmpDetails>
     </Employee>
 
Above XMLis stored as a column(DATA) with data type [XML NULLABLE] in a table in DB2. Assume that the structure of the table is something like this:
 
      Table name:  REGEVENT
     Columns are: REFID (VARCHAR), APPID(VARCHAR), DATA(XML NULLABLE)
 
Suppose the value in the table is: REFID(12345), APPID(54321), DATA(Employee xml as mentioned above).
 
Now I have to get the value of element in the XML stored in column DATA using Xquery (Or any other way is also fine).
 
I am trying the following query, but I am getting the value EmpName as NULL.
 
select XMLCAST(XMLQUERY('$d/Employee/EmpDetails/Name' PASSING rg.DATA AS "d") AS VARCHAR(50)) AS EmpName from REGEVENT  rg where REFID='12345';

原文：https://stackoverflow.com/questions/21087022