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Category: MS SQL
Hits: 918
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')

Details
Category: MS SQL
Hits: 998
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.

Details
Category: MS SQL
Hits: 2477
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)))

Details
Category: MS SQL
Hits: 1592
Here are few "DROP IF EXISTS" SQL statements, for my future reference.

Trigger from sys.objects: 

IF EXISTS (SELECT * FROM sys.objects WHERE [name] = N'myTrigger' AND [type] = 'TR')
BEGIN
      DROP TRIGGER [dbo].[myTrigger];
END;
GO
Stored procedure with OBJECT_ID: 
IF OBJECT_ID('dbo.mySP') IS NOT NULL
  DROP PROCEDURE dbo.mySP
GO
Temp table: 
IF OBJECT_ID('tempdb..#myTempTable') IS NOT NULL DROP TABLE #myTempTable
GO
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