SQL Server XQuery Methods

Sql Server provides xquery methods to query xml file or xml data. Using these methods we can Insert, Update, Delete data in xml file or in XML Data Type variable. In Sql Server XQuery statements are case sensitive since xml is case sensitive. Hence while query to xml data remember this thing.

XQuery Methods

we have following xml data to implement all the XQuery methods given below.

1. xml.exist()

   This method returns a boolean value depends upon the condition in this method like as

    SELECT @xml.exist('/Suppliers/User[@Email = "[email protected]"]') as Result1
   SELECT @xml.exist('/Suppliers/User[@Email = "[email protected]"]') as Result2 

   

2. xml.query()

   This method takes an XQuery statement and returns an instance of the XML data type like as

    SELECT @xml.query('/Suppliers/User') as Users 

   

    SELECT @xml.query('distinct-values( data(/Suppliers/User/Item/@No))') as Items 

   

3. xml.value()

   This method takes an XQuery statement and returns a single value after type casting like as

    SELECT @xml.value('/Suppliers[1]/User[1]/@Email', 'VARCHAR(20)') as ResultEmail1
   SELECT @xml.value('/Suppliers[1]/User[2]/@Email', 'VARCHAR(20)') as ResultEmail2 

   

4. xml.nodes()

   This method takes an XQuery statement and returns a single value after type casting like as

    SELECT x.value('@UserNo', 'int') AS UserNo, x.value('@Email', 'varchar(50)') AS Email
   FROM @xml.nodes('/Suppliers/User') TempXML (x)
    SELECT x.value('../@UserNo', 'int') AS UserNo, x.value('../@Email', 'varchar(50)') AS Email, x.value('@Name', 'varchar(50)') AS ItemName
   FROM @xml.nodes('/Suppliers/User/Item') TempXML (x)

   

5. xml.modify()

   This method takes an XQuery statement and modify the xml data like as

    --Insert node in the end of XML 
   SET @xml.modify ('insert  as last into (/Suppliers)[1]')
   SELECT @xml;

   

    --Update node in xml
   DECLARE @UserNo int =120
   SET @xml.modify ('replace value of (/Suppliers/User/@UserNo)[1] with sql:variable("@UserNo")')
   SELECT @xml;

   

    --Update node in xml conditionally
   SET @xml.modify(' replace value of (/Suppliers/User/@UserNo)[1] with ( if (count(/Suppliers/User[1]/Item) > 2) then "3.0" else "1.0" ) ')
   SELECT @xml;

   

    --Delete node in xml SET @xml.modify(' delete Suppliers/User/Item[@No=1]')
   SELECT @xml;

   

    --Delete node in xml depends on condition
   DECLARE @ItemNo int=1
   SET @xml.modify(' delete Suppliers/User/Item[@No=sql:variable("@ItemNo")]')
   SELECT @xml;

   

Summary

In this article I try to explain the Sql Server XQuery methods with example. I hope after reading this article you will be able to query xml in Sql Server. I would like to have feedback from my blog readers. Please post your feedback, question, or comments about this article.

Further Reading