Shredding XML in SQL Server 2005

Using XML data has many applications. In databases in particular it can be used for passing parameters from client applications, exchange data between SQL modules, or storing details in XML columns. SQL Server 2005 offers new capabilities and native support for XML. Below is one example of utilizing some of the new XML methods in XML to shred XML data to table format.

-- Declare XML variable

DECLARE @data XML;

 

-- Element-centered XML

SET @data =

N'<data>

    <customer>

      <id>1</id>

      <name>Allied Industries</name>

    </customer>

    <customer>

      <id>2</id>

      <name>Trades International</name>

    </customer>

  </data>';

 

-- Using the query() method

SELECT T.customer.query('id').value('.', 'INT') AS customer_id,

       T.customer.query('name').value('.', 'VARCHAR(20)') AS customer_name

FROM @data.nodes('data/customer') AS T(customer);

 

-- Using the value() method

SELECT T.customer.value('(id)[1]', 'INT') AS customer_id,

       T.customer.value('(name)[1]', 'VARCHAR(20)') AS customer_name

FROM @data.nodes('data/customer') AS T(customer);

 

-- Select only customer which id equals 2 using the exist() method

SELECT T.customer.value('(id)[1]', 'INT') AS customer_id,

       T.customer.value('(name)[1]', 'VARCHAR(20)') AS customer_name

FROM @data.nodes('data/customer') AS T(customer)

WHERE T.customer.exist('id/text()[. = "2"]') = 1;

 

-- Attribute-centered XML

SET @data =

N'<data>

    <customer id="1" name="Allied Industries"/>

    <customer id="2" name="Trades International"/>

  </data>';

 

-- Using the value() method

SELECT T.customer.value('@id', 'INT') AS customer_id,

       T.customer.value('@name', 'VARCHAR(20)') AS customer_name

FROM @data.nodes('data/customer') AS T(customer);

 

 

-- Results

customer_id customer_name

----------- --------------------

1           Allied Industries

2           Trades International

Testing the processing for element-centered XML versus attribute-centered XML does show that attribute-centered XML is processed faster.

Resources:

XML Support in Microsoft SQL Server 2005
http://msdn2.microsoft.com/en-us/library/ms345117.aspx

9 replies
  1. shh
    shh says:

    This (attribute based) select statement works also.
    Any signficant difference?
    I stumbled upon it, converting a element based statement to attribute based.

    SELECT T.customer.value(‘@id[1]’, ‘INT’) AS customer_id, T.customer.value(‘@name[1]’, ‘VARCHAR(20)’) AS customer_name FROM @data.nodes(‘data/customer’) AS T(customer);

    Don’t forget about this Sql Server 2005 (SP2) issue.

    It seems to still be an issue in 2008, despite “Tomer”‘s remarks to the contrary.

    Reply
  2. shh
    shh says:

    This (attribute based) select statement works also.
    Any signficant difference?
    I stumbled upon it, converting a element based statement to attribute based.

    SELECT T.customer.value(‘@id[1]’, ‘INT’) AS customer_id, T.customer.value(‘@name[1]’, ‘VARCHAR(20)’) AS customer_name FROM @data.nodes(‘data/customer’) AS T(customer);

    Don’t forget about this Sql Server 2005 (SP2) issue.
    http://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=250407

    It seems to still be an issue in 2008, despite “Tomer”‘s remarks to the contrary.

    Reply
  3. Plamen Ratchev
    Plamen Ratchev says:

    Hi shh,

    Although your query produces the same results, it is not technically equivalent path expression to the one I posted. The query that you posted uses the position predicate [1] to pull the first occurrence. However, in attribute-centered XML you cannot have duplicate attributes, so essentially the results will be the same.

    Yes, I am aware of the feedback item posted by Erland Sommarskog and voted long time ago. Hope we see that resolved.

    Reply
  4. Anonymous
    Anonymous says:

    Is this the best approach

    CREATE TABLE [dbo].[UserAuditLog](
    [UserAuditLogGUID] varchar NOT NULL,default newid()
    [UserPersonGUID] varchar NOT NULL,
    [UserID] varchar NOT NULL,
    [UserName] varchar NOT NULL,
    [RoleID] varchar NULL,
    [RoleName] varchar NULL,
    [ActionTaken] varchar NOT NULL,
    [CreatedBy] varchar NOT NULL,
    [CreatedByPersonGUID] varchar NOT NULL,
    [DateRecorded] [datetime] NOT NULL, getdate()
    ) ON [PRIMARY]

    CREATE PROCEDURE [dbo].[InsertUserAuditLog]
    (
    @UserAuditLog xml
    )
    AS
    BEGIN
    SET NOCOUNT ON
    DECLARE @ErrMsg varchar(4000)
    ,@ErrSeverity int = 16
    ,@v_UserID varchar(25) = NULL
    ,@v_UserPersonGUID varchar(128) = NULL
    ,@v_UserName varchar(128) = NULL
    ,@v_CreatedByPersonGUID varchar(128) = NULL
    ,@v_CreatedBy varchar(128) = NULL
    ,@v_RoleID varchar(200) = NULL
    ,@v_RoleName varchar(2000)= NULL
    ,@v_ActionTaken varchar(1000)= NULL

    BEGIN TRY
    — Retrieving XMLvalues into Local Variables
    SELECT
    @v_UserID = LogInfo.Item.query('./UserID') .value('.','varchar(25)') ,
    @v_UserPersonGUID = LogInfo.Item.query('./UserPersonGUID') .value('.','varchar(128)') ,
    @v_UserName = LogInfo.Item.query('./UserName') .value('.','varchar(128)'),
    @v_CreatedByPersonGUID= LogInfo.Item.query('./CreatedByPersonGUID').value('.','varchar(128)'),
    @v_CreatedBy = LogInfo.Item.query('./CreatedBy') .value('.','varchar(128)'),
    @v_RoleID = LogInfo.Item.query('./RoleID') .value('.','varchar(200)'),
    @v_RoleName = LogInfo.Item.query('./RoleName') .value('.','varchar(2000)'),
    @v_ActionTaken = LogInfo.Item.query('./ActionTaken') .value('.','varchar(1000)')
    FROM @UserAuditLog.nodes('/UserAuditLog') AS LogInfo(Item)

    –Validating input parameters.

    INSERT INTO CHR.dbo.UserAuditLog(
    UserAuditLogGUID
    ,UserPersonGUID
    ,UserID
    ,UserName
    ,RoleID
    ,RoleName
    ,ActionTaken
    ,CreatedBy
    ,CreatedByPersonGUID
    ,DateRecorded
    )
    values
    (@v_UserPersonGUID
    ,@v_UserID
    ,@v_UserName
    ,@v_RoleID
    ,@v_RoleName
    ,@v_ActionTaken
    ,@v_CreatedBy
    ,@v_CreatedByPersonGUID
    )
    END TRY
    BEGIN CATCH
    — Raise an error with the details of the exception
    SELECT @ErrMsg = ERROR_MESSAGE()
    RAISERROR(@ErrMsg, @ErrSeverity, 1)
    END CATCH
    END

    Reply
  5. Plamen Ratchev
    Plamen Ratchev says:

    Instead of storing the XML data in variables you can directly insert it, like this:

    INSERT INTO CHR.dbo.UserAuditLog(
    UserPersonGUID
    ,UserID
    ,UserName
    ,RoleID
    ,RoleName
    ,ActionTaken
    ,CreatedBy
    ,CreatedByPersonGUID)
    SELECT
    LogInfo.Item.query('./UserPersonGUID') .value('.','varchar(128)') ,
    LogInfo.Item.query('./UserID') .value('.','varchar(25)') ,
    LogInfo.Item.query('./UserName') .value('.','varchar(128)'),
    LogInfo.Item.query('./RoleID') .value('.','varchar(200)'),
    LogInfo.Item.query('./RoleName') .value('.','varchar(2000)'),
    LogInfo.Item.query('./ActionTaken') .value('.','varchar(1000)'),
    LogInfo.Item.query('./CreatedBy') .value('.','varchar(128)'),
    LogInfo.Item.query('./CreatedByPersonGUID').value('.','varchar(128)')
    FROM @UserAuditLog.nodes('/UserAuditLog') AS LogInfo(Item);

    Reply
  6. Moad El Ouali
    Moad El Ouali says:

    In case of only one element like the folowing example :

    "< root>
    < subroot> info1
    < subroot> info1
    < subroot> info1
    < subroot> info1
    "

    it returns empty fields, I don't know how to fix it, any ideas please?

    Reply

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published.