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SQL Server XML Data Type

SQL Server XML Data Type

24 Mar 2024
16 min read

SQL Server XML Data Type: An Overview

SQL Server's XML data type allows for the storage and manipulation of XML data within the database, making it easier to query, change, and transform XML documents directly within SQL queries. Consider taking a SQL Server Tutorial or enrolling in a SQL Server Certification Course to gain a better understanding and mastery of XML processing in SQL Server.

XML Data Type in SQL Server

XML data type was introduced in SQL Server 2005 to work with XML data. Using this data type, we can store XML in its native format and can also query/modify the XML data within the xml. We can use xml data types like:
  1. Variable
  2. Field/Column in a table
  3. Parameter in the user-defined function (UDF) or stored procedure(SP)
  4. Return value from a UDF or SP

We can define xml data type field to NOT NULL or we can provide a default value to it.

Different XML Data Types Methods

SQL Server supports five XML data type methods for extracting and manipulating XML data.

  1. Query()
  2. Value()
  3. Exist()
  4. Modify()
  5. Nodes()

1. Query() Method

The query() method allows you to connect XPath expressions to an XML instance stored in an XML data type column. It treats XML data like a tiny database, allowing you to query specific components or characteristics using XPath syntax.


DECLARE @xml xml = N'<bookstore>
 <book genre="fantasy">
  <title>The Lord of the Rings</title>
 <book genre="sci-fi">
  <title>Ender\'s Game</title>

SELECT b.value('@genre', 'nvarchar(50)') AS Genre, b.value('(title/text())[1]', 'nvarchar(max)') AS Title
FROM @xml.query('//book') AS b;

This example uses XPath expressions in the query() function to obtain the genre attribute and text content of the first <title> element within each <book> element.

2. Value() Method

The value() method returns a single value of a certain data type from an XML object. It accepts two arguments: the XPath expression for locating the element or attribute, and the data type for the returned value.


DECLARE @xml xml = N'<order id="123">
 <customer name="John Doe" />
  <item name="Book" price="19.99" />

SELECT @xml.value('//customer/@name', 'nvarchar(50)') AS CustomerName,
   @xml.value('//items/item/@price', 'decimal(5,2)') AS ItemPrice;

This example uses value() to extract the name property from the <customer> element and the price attribute from the first <item> element.

3. Exist() Method

The exist() method determines whether an XPath expression returns any nodes within the XML instance. It returns 1 if nodes are detected, and 0 otherwise.


DECLARE @xml xml = N'<document>
 <section>Data Analysis</section>
 <section>Machine Learning</section>

SELECT CASE WHEN @xml.exist('//section[@name="Database"]') = 1 THEN 'Section exists' ELSE 'Section does not exist' END AS Result;

This example uses exist() to check if the XML document contains a section> element with the name property set to "Database".

4. Modify() Method

The modify() method lets you change the structure and content of XML data using XML Data Modification Language (XML DML) commands. These statements encompass insert, update, remove, and replace operations for specified items or attributes.


DECLARE @xml xml = N'<product id="100">

SELECT @xml.modify('insert <size>Large</size> after /product/color');

In this example, alter() is used to place a new <size> element with the text "Large" after the < color> element within the <product> element.

5. Nodes() Method

The nodes() method "shreds" XML data into a relational database structure. It treats each element or property in the XPath query as a distinct row. This makes it easier to work with XML data using conventional T-SQL queries.


DECLARE @xml xml = N'<bookstore>
 <book genre="fantasy">
  <title>The Hobbit</title>
 <book genre="sci-fi">

SELECT * FROM @xml.nodes('//book') AS b(Genre nvarchar(50), Title nvarchar(max));

This example uses nodes() to generate a result set with two columns, "Genre" and "Title," for each <book> element in the XML data.

Advantages of using XML data type in SQL Server

  • XML is used to store unstructured data in a relational database.
  • XML itself checks the information inside the file with tags and their values using DTD (Document Type Definition) and schema.
  • XML data type holds independent data structures, therefore it can be readily merged or used in other database sources.
  • In a way, the XML data type decreases the back-end application burden because XML is easily used with a UI.
  • XML data type can be used with the input argument in a function or stored procedure.

Disadvantages of using XML data with SQL Server

  • In SQL Server data pages, the XML data type takes up more space than the relational (row/column) format since it is redundant with the XML tag-value set.
  • In comparison to a normalized structure, query execution, and data manipulation may take longer.
  • Large XML documents require additional server resources, including CPU, memory, and IO, in SQL Server.
  • Additionally, the XML query format is complex.

Limitation Of XML Data type

  • We can’t directly compare an instance of the XML data type to another instance of the XML data type. For equality comparisons, we first need to convert the XML type to a character type.
  • We can’t use GROUP BY or ORDER BY with an XML data type column.
  • We can’t use XML data type field as a primary key, Unique key, or foreign key.
  • We can’t define the XML data type field with the COLLATE keyword.

Query XML Data

Suppose we have the following tables in the database. Using these tables we will produce query results as an xml

CREATE TABLE Department (
 DeptID int IDENTITY(1,1) primary key ,
 DeptName varchar(50) NULL,
 Location varchar(50) NULL )
 EmpName varchar(50) NULL,
 Address varchar(100) NULL,
 DeptID int foreign Key references Department(DeptID) 
--Now Insert data into these tables
INSERT INTO Department (DeptName,Location)VALUES('HR','Delhi')
INSERT INTO Department (DeptName,Location)VALUES('IT','Delhi')
INSERT INTO Department (DeptName,Location)VALUES('Technical','Delhi')
INSERT INTO Employee( EmpName,Address,DeptID)VALUES('Shailendra','Noida',2)
INSERT INTO Employee( EmpName,Address,DeptID)VALUES('Mohan','Noida',2)
INSERT INTO Employee( EmpName,Address,DeptID)VALUES('Vipul','Noida',1)
INSERT INTO Employee( EmpName,Address,DeptID)VALUES('Mrinal','Noida',3) 

We can retrieve data table records as xml data using the FOR XML clause in the SELECT statement. In the FOR XML Clause, we can define three xml modes.


It generates output with both element and attribute features in combination with a sub-query.

SELECT DeptName, EmpID
FROM Employee AS Emp JOIN Department AS Dept
ON Emp.DeptID= Dept.DeptID
This SQL query retrieves the Department Name and Employee ID from the Employee table, joins them with the Department table using matching Department IDs, then formats the output as XML with nested components for each entry.
 <Dept DeptName="IT">
 <Emp EmpID="1" />
 <Emp EmpID="2" />
<Dept DeptName="HR">
 <Emp EmpID="3" />
<Dept DeptName="Technical">
 <Emp EmpID="4" />
 <Emp EmpID="5" />


It converts the rowset which is the result of the query execution, into an XML document. This mode provides more control over the format of the XML, which means in which format you want xml you need to define that format in a select query.

 1 tag,
 NULL parent,
 EmpID [employee!1!ID],
 EmpName [employee!1!name],
 NULL [order!2!date],
 NULL [department!3!name]
FROM Employee
FROM Employee e JOIN Department d
ON e.DeptID=d.DeptID
This SQL query collects employee and department data, assigns tags and parent relationships for XML production, sorts by employee ID, and formats as XML with explicit structure.
<employee ID="1" name="Shailendra">
 <department name="IT" />
<employee ID="2" name="Mohan">
 <department name="IT" />
<employee ID="3" name="Vipul">
 <department name="HR" />
<employee ID="4" name="Mrinal">
 <department name="Technical" />
<employee ID="5" name="Jitendra">
 <department name="Technical" />


It produces a single element the optionally provided element name for each row in the query result set that is returned by a select statement.

SELECT Emp.EmpID, Dept.DeptName
Employee as Emp JOIN Department as Dept
ON Emp.DeptID= Dept.DeptID
This SQL query collects Employee IDs and corresponding Department Names by connecting the Employee and Department tables based on matching Department IDs, and then prepares the output as XML using a simple row-based structure in RAW mode.
<row EmpID="1" DeptName="IT" />
<row EmpID="2" DeptName="IT" />
<row EmpID="3" DeptName="HR" />
<row EmpID="4" DeptName="Technical" />
<row EmpID="5" DeptName="Technical" /> 

Read More


In this article, I try to explain the XML Data Type with examples. I hope after reading this article you will be aware of XML Datatype in Sql Server. I would like to have feedback from my blog readers. Please post your feedback, questions, or comments about this article.


Q1. What is SQL Server's XML data type?

The SQL Server XML data type enables for the storage and manipulation of XML data within the database, making it easier to store and retrieve structured content.

Q2. How can I store XML data in SQL Server?

You can store XML documents directly in SQL Server by defining a column with the XML data type or using XML data type variables.

Q3. Can I query XML data in SQL Server?

Yes, SQL Server has built-in support for querying XML data using XPath or XQuery expressions to get specific items or attributes.

Q4. How can I alter XML data in SQL Server?

SQL Server's XML data can be updated by calling methods such as .modify() to add, delete, or edit components or attributes within XML documents.

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About Author
Shailendra Chauhan (Microsoft MVP, Founder & CEO at Scholarhat by DotNetTricks)

Shailendra Chauhan is the Founder and CEO at ScholarHat by DotNetTricks which is a brand when it comes to e-Learning. He provides training and consultation over an array of technologies like Cloud, .NET, Angular, React, Node, Microservices, Containers and Mobile Apps development. He has been awarded Microsoft MVP 8th time in a row (2016-2023). He has changed many lives with his writings and unique training programs. He has a number of most sought-after books to his name which has helped job aspirants in cracking tough interviews with ease.
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