Extracting value from XML in SQL Server

Question

I'm trying to write a SQL Server query to select values from a XML column.

The column messagebody (type XML ) has content like this:

<?xml version="1.0" encoding="utf-16"?>
<GetActivityUnemploymentGenerelEventType xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <ActivityItem xmlns="http://service.bmuuuu/">
        <ActivityCoreItem xmlns="http://service.bmxxxx">
            <ActivityIdentifier xmlns="http://service.bmyyyy">d5ck7132-703c-1234-8099-963b35b24bc5</ActivityIdentifier>
            <StartDate xmlns="http://service.bmaaa">2016-01-25</StartDate>

I'm trying to nail the value of startdate and ActivityIdentifier .

I've tried several solution fx:

SELECT XML.query('messagebody(/GetActivityUnemploymentGenerelEventType/ActivityItem/ActivityCoreItem/ActivityIdentifier)')
FROM table

SELECT messagebody.value('(/GetActivityUnemploymentGenerelEventType/ActivityCoreItem/ActivityIdentifier/Value)[1]', 'int')
FROM table

SELECT messagebody.value('(/GetActivityUnemploymentGenerelEventType//ActivityCoreItem/ActivityIdentifier())[1]', 'nvarchar(max)')
FROM table

Query result:

Cannot find either column "messagebody" or the user-defined function or aggregate "messagebody.value", or the name is ambiguous.

Any suggestions?

Answer 1

You're not respecting the existing XML namespaces in your XML document! You need to include those in your XQuery - try this:

;WITH XMLNAMESPACES ('http://service.bmuuuu/' AS ns1, 
                     'http://service.bmxxxx' AS ns2, 
                     'http://service.bmyyyy' as ns3, 
                     'http://service.bmaaa' as ns4)
SELECT
    ActivityIdentifier = xc.value('(ns3:ActivityIdentifier)[1]', 'varchar(100)'),
    StartDate = xc.value('(ns4:StartDate)[1]', 'varchar(25)')
FROM 
    dbo.YourTable
CROSS APPLY
    MessageBody.nodes('/GetActivityUnemploymentGenerelEventType/ns1:ActivityItem/ns2:ActivityCoreItem') AS XT(XC)