XML DML (Data Modification Language) - SQL Server

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Written by: Stanko Milosev
Category: MS SQL
Hits: 318
Here is my example of XML modification language in SQL Server. First lets say we have a table like: 
CREATE TABLE [dbo].[XmlModificationLanguageExample](
	[ID] [uniqueidentifier] NOT NULL,
	[XmlField] [xml] NULL,
 CONSTRAINT [PK_XmlModificationLanguageExample] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
Final goal is to have XML like: 
<root>
	<Parent Name="IamFather" Kind="Father">
		<Value Name="Oldest" Type="Father" Value="True"/>
		<Value Name="Kids" Type="Children" Value="
				<root>
					<Parent Name="IamTheSonOfMyFather" Kind="Father">
						<Value Name="Oldest" Type="Father" Value="True"/>
						<Value Name="MyKids" Type="Geni.Files" Value="
								<root>
									<Children Kind="Male" Count="12" ChildName="Stanko">
										<Value Name="Name" Type="Male.Child" Value="48yrsOld"/>
									</Children>
								</root>
						" />
					</Parent>
				</root>
		" />
  </Parent>
</root>
First, lets insert XML like: 
<root>
	<Parent Name="IamFather" Kind="Father">
		<Value Name="Oldest" Type="Father" Value="True"/>
		<Value Name="Kids" Type="Children" Value="" />
  </Parent>
</root>

INSERT INTO [dbo].[XmlModificationLanguageExample]
           ([ID]
           ,[XmlField])
     VALUES
           (NEWID()
           , '<root>
	<Parent Name="IamFather" Kind="Father">
		<Value Name="Oldest" Type="Father" Value="True"/>
		<Value Name="Kids" Type="Children" Value="" />
  </Parent>
</root>')
Now first I am gonna prepare XML which I will insert into the node: 
<Value Name="Kids" Type="Children" Value="" />

DECLARE @FatherXML XML = '<root>
	<Parent Name="IamTheSonOfMyFather" Kind="Father">
		<Value Name="Oldest" Type="Father" Value="True"/>
		<Value Name="MyKids" Type="Geni.Files" Value="" />
  </Parent>
</root>';

DECLARE @Kids nvarchar(max) = '<root>
	<Children Kind="Male" Count="12" ChildName="Stanko">
		<Value Name="Name" Type="Male.Child" Value="48yrsOld"/>
	</Children>
</root>';

SET @FatherXML.modify('
    replace value of (
       /root/Parent[@Name="IamTheSonOfMyFather"]
	   /Value[@Name="MyKids"]/@Value)[1]
    with (sql:variable("@Kids") cast as xs:string?)
');

select @FatherXML;
Here notice that @Kids is of type nvarchar(max), where @FatherXML is of type XML Now that XML I will insert into main XML, and update the table in server: 
DECLARE @FatherAsString NVARCHAR(MAX) = CONVERT(NVARCHAR(MAX), @FatherXML);

UPDATE XmlModificationLanguageExample
SET XmlField.modify('
    replace value of (
		/root/Parent[@Name="IamFather"]
	   /Value[@Name="Kids"]/@Value)[1]
    with (sql:variable("@FatherAsString") cast as xs:string?)
')
WHERE ID = '4D14CD89-002F-4985-B54E-CA2CC0DA6913';

select * from XmlModificationLanguageExample
Here notice that I am converting @FatherXML to NVARCHAR(MAX), and like this I updating attribute. Now, lets say that between nodes: 
<Value Name="Oldest" Type="Father" Value="True"/>
<Value Name="Kids" Type="Children" Value="" />
I want to add new node: 
<Value Name="Youngest" Type="Father" Value="True"/>
after "Oldest": 
UPDATE XmlModificationLanguageExample
SET XmlField.modify('
    insert sql:variable("@YoungestXML")
    after (
        /root/Parent[@Name="IamFather"]
		/Value[@Name="Oldest"]
    )[1]
')
WHERE ID = '4D14CD89-002F-4985-B54E-CA2CC0DA6913';

select * from XmlModificationLanguageExample
Here is the whole SQL query: 
IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[XmlModificationLanguageExample]') AND type in (N'U'))
DROP TABLE [dbo].[XmlModificationLanguageExample]
GO

CREATE TABLE [dbo].[XmlModificationLanguageExample](
	[ID] [uniqueidentifier] NOT NULL,
	[XmlField] [xml] NULL,
 CONSTRAINT [PK_XmlModificationLanguageExample] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO

DECLARE @ID uniqueidentifier = NEWID();

INSERT INTO [dbo].[XmlModificationLanguageExample]
           ([ID]
           ,[XmlField])
     VALUES
           (@ID
           , '<root>
	<Parent Name="IamFather" Kind="Father">
		<Value Name="Oldest" Type="Father" Value="True"/>
		<Value Name="Kids" Type="Children" Value="" />
  </Parent>
</root>')

DECLARE @FatherXML XML = '<root>
	<Parent Name="IamTheSonOfMyFather" Kind="Father">
		<Value Name="Oldest" Type="Father" Value="True"/>
		<Value Name="MyKids" Type="Geni.Files" Value="" />
  </Parent>
</root>';

DECLARE @Kids nvarchar(max) = '<root>
	<Children Kind="Male" Count="12" ChildName="Stanko">
		<Value Name="Name" Type="Male.Child" Value="48yrsOld"/>
	</Children>
</root>';

SET @FatherXML.modify('
    replace value of (
       /root/Parent[@Name="IamTheSonOfMyFather"]
	   /Value[@Name="MyKids"]/@Value)[1]
    with (sql:variable("@Kids") cast as xs:string?)
');

SELECT @FatherXML AS FatherXmlData;

DECLARE @FatherAsString NVARCHAR(MAX) = CONVERT(NVARCHAR(MAX), @FatherXML);

UPDATE XmlModificationLanguageExample
SET XmlField.modify('
    replace value of (
		/root/Parent[@Name="IamFather"]
	   /Value[@Name="Kids"]/@Value)[1]
    with (sql:variable("@FatherAsString") cast as xs:string?)
')
WHERE ID = @ID;

select * from XmlModificationLanguageExample

DECLARE @YoungestXML XML = '<Value Name="Youngest" Type="Father" Value="True"/>'

UPDATE XmlModificationLanguageExample
SET XmlField.modify('
    insert sql:variable("@YoungestXML")
    after (
        /root/Parent[@Name="IamFather"]
		/Value[@Name="Oldest"]
    )[1]
')
WHERE ID = @ID;

select * from XmlModificationLanguageExample

Generate XML with attributes

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Written by: Stanko Milosev
Category: MS SQL
Hits: 1837
Recently I had task to generate XML which is supposed to look something like this: 
<NamesTree>
  <TypeOfName Name="Test" Kind="TestNames">
    <Value Name="FirstName" Type="nvarchar(50)" Value="John" />
    <Value Name="LastName" Type="nvarchar(50)" Value="Doe" />
    <Value Name="Type" Type="int" Value="1" />
  </TypeOfName>
  <TypeOfName Name="Test" Kind="TestNames">
    <Value Name="FirstName" Type="nvarchar(50)" Value="Jane" />
    <Value Name="LastName" Type="nvarchar(50)" Value="Doe" />
    <Value Name="Type" Type="int" Value="2" />
  </TypeOfName>
</NamesTree>
This is how my table look like: 
CREATE TABLE [dbo].[Test](
	[FirstName] [nvarchar](50) NULL,
	[LastName] [nvarchar](50) NULL,
	[Type] [int] NULL
) ON [PRIMARY]
First I am gonna seed my table: 
insert into test values ('John', 'Doe', 1)
insert into test values ('Jane', 'Doe', 2)
This is how SQL looks like: 
select 
	'Test' '@Name'
	, 'TestNames' '@Kind'
	, 'FirstName' [Value/@Name]
	, 'nvarchar(50)' 'Value/@Type'
	, FirstName 'Value/@Value'
	, null
	, 'LastName' [Value/@Name]
	, 'nvarchar(50)' 'Value/@Type'
	, LastName 'Value/@Value'
	, null
	, 'Type' [Value/@Name]
	, 'int' 'Value/@Type'
	, Type 'Value/@Value'
	, null
from test
for XML path('TypeOfName'), root('NamesTree')

Select from XML

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Written by: Stanko Milosev
Category: MS SQL
Hits: 1919
One example on how to select values from XML in MS SQL: 
declare @myXml xml = 
'
<params>
    <param>
        <value>
            <array>
                <data>
                    <value>
                        <string>NameOfValueOne</string>
                    </value>
                    <value>
                        <string>ValueOne</string>
                    </value>
                </data>
            </array>
        </value>
    </param>
    <param>
        <value>
            <array>
                <data>
                    <value>
                        <string>NameOfValueTwo</string>
                    </value>
                    <value>
                        <string>ValueTwo</string>
                    </value>
                </data>
            </array>
        </value>
    </param>
</params>
'

select 
	T.N.value('.', 'varchar(max)') Value
from @myXml.nodes('/params/param/value/array/data/value') T(N)
One more example: 
declare @myXml xml = 
'
    <param>
        <value Name="TestNameValue1" Type="TestType1" Value="TestValue1"></value>
        <value Name="TestNameValue2" Type="TestType1" Value="TestValue2"></value>
    </param>
    <param>
        <value Name="TestNameValue1" Type="TestType2" Value="TestValue3"></value>
        <value Name="TestNameValue2" Type="TestType2" Value="TestValue4"></value>
    </param>
'

select 
	T.N.value('(value[@Name="TestNameValue1"]/@Value)[1]', 'varchar(max)') TestNameValue1
	, T.N.value('(value[@Name="TestNameValue2"]/@Value)[1]', 'varchar(max)') TestNameValue2
from @myXml.nodes('/param') T(N)

Another example with OpenXML: 

declare @myXml xml =
'
    <params>
		<param>
			<value Name="TestNameValue1" Type="TestType1" Value="TestValue1"></value>
			<value Name="TestNameValue2" Type="TestType1" Value="TestValue2"></value>
		</param>
		<param>
			<value Name="TestNameValue1" Type="TestType2" Value="TestValue3"></value>
			<value Name="TestNameValue2" Type="TestType2" Value="TestValue4"></value>
		</param>
    </params>
'
 
declare @myXmlDoc int
exec sp_xml_preparedocument @myXmlDoc out, @myXml, '<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>'

select TestNameValue1, 
       TestNameValue2
from openxml(@myXmlDoc, '/params/param', 2) 
  with (
         TestNameValue1  varchar(max) '(value[@Name="TestNameValue1"]/@Value)[1]'
		, TestNameValue2 varchar(max) '(value[@Name="TestNameValue2"]/@Value)[1]'
       )

exec sp_xml_removedocument @myXmlDoc

Here have I found:

As far as performance differences between OPENXML and the XML column type with the nodes() function, there doesn't seem to be a crystal clear answer. If you scan through the SQL Server XML posts on the internet you will find some threads where OPENXML is faster than the XML column's nodes() function and vice-versa. As always the best approach may vary depending on your individual circumstances so don't blindly choose the XML column type and the nodes() function over OPENXML.

Log in trigger

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Written by: Stanko Milosev
Category: MS SQL
Hits: 3337
One my example how to log messages in trigger.

Create table: 

create table log (tableName varchar(max), msg varchar(max))
Log in trigger: 
declare @xml XML

set @xml = (select * from deleted for xml auto, elements )
insert into log(tableName, msg) values('deleted', cast(@xml as varchar(max)))
  1. Drop if exists
  2. The login already has an account under a different user name.
  3. Access SQL Server from other machines
  4. How to change sa password.

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