How to properly use XML parameter for Update procedure in SQL Server

Question

I am pretty new to XML and am looking for a way to use XML from an input parameter for the below part of a stored procedure (using SQL Server 2012). The XML is submitted via

Answer 1

Try updating like this.

UPDATE A
SET    title = b.title,
       summary = b.summary,
       post = b.post,
       departmentID = b.departmentID
FROM   RC_Posts A
       JOIN (SELECT title=[Xml_Tab].[Cols].value('(title)[1]', 'nvarchar(100)'),
                    summary=[Xml_Tab].[Cols].value('(summary)[1]', 'nvarchar(500)'),
                    post=[Xml_Tab].[Cols].value('(post)[1]', 'nvarchar(max)'),
                    departmentID=[Xml_Tab].[Cols].value('(departmentID)[1]', 'int'),
                    PostID=[Xml_Tab].[Cols].value('(postID)[1]', 'int')
             FROM   @xmlMain.nodes('/root') AS [Xml_Tab]([Cols])) B
         ON a.postID = b.postID