IN2BI

Change Data Capture (CDC) is an enterprise feature of SQL Server since version 2008. ¹² It's a non not very intrusive way to collect only the changes in selected tables of your source system.³ And thus providing a way to effectively handle your data warehouse load.

Integration Services (SSIS) and CDC

To handle these changes you can roll your own SSIS-CDC system where you choose where you save the state of the rows that you handled.⁴  Since 2012 it's more convenient to use the new CDC components that Microsoft shipped with SQL Server 2012.

There are three CDC components:

• CDC Control task is used to control the life cycle of change data capture (CDC) packages. It handles the management of Log Sequence Number (LSN) ranges that are processed in a run of a CDC package.
• CDC Source, reads a range of change data from change tables and delivers the changes downstream to other SSIS components.
• CDC Splitter, splits a single flow of rows from a CDC source data flow into different flows of rows for Insert, Update and Delete operations

BIML

These new components are implemented as custom components and aren't natively handled in BIML. So to use them in a BIML solution you have to do some extra work.

Whenever I create a BIML solution I have a three step approach:

1. Create a package in SSIS (Or at least a design)
2. Create a BIML file that can create the package (without script)
   I call this the vanilla version.
3. Gather meta data if not already available and add script to the BIML file(s) to create all the packages

For this blog post I'll focus on step 2. Matt Mason of Microsoft already wrote a nice walkthrough that serves well for step 1. Step 3 is something for a future blog post or a sponsor.

Preparing the environment

If you didn't follow the walkthrough by Matt Mason you need to create the environment with SQL Server Management Studio:

1. Create a database (CDCTest)
2. Create the DimDepartmentGroup_CDC table that will be used as a source.
3. Enable CDC for the database
4. Add a primary key to the table created in step 2.
5. Enable CDC for the DimDepartment_CDC table that was created in step 2
6. Create a destination table
7. Create a table to store the cdc state

If you did follow the walkthrough skip step 1,3 and 7

The necessary T-SQl code (available at GitHub Gist):

Creating the BIML file for the initial load

The initial load package is relatively simple. This is an overview of the resulting package with the CDC Components marked in yellow.

Control Flow	Data Flow

The hard part in this code is getting the necessary information for the CDC Control Task. You'll typically find itin the XML code of the vanilla package I described earlier. Open this package by clicking View Code in the context menu (F7) and find the CDC ControlTask

In this xml snippet you'll find the CreationName, an required attribute of the CustomTask in Biml. The marked ObjectData snippet can be copied into an CData tag within the ObjectData node of the CustomTask.

Creating the BIML file for the incremental load

In the incremental load we will use the CDC Data Flow Components. A complicating factor in creating the BIML file is the necessity of meta data of columns. Column information can normally be queried by BIML/SSIS. For these custom components we have to provide them. Before creating the BIML let's look at the resulting package:

Control Flow	Data Flow

Some remarks:

The CDC Control Tasks will typically handle changes of more than one table. For now I've implemented this using a separate sequence container for the DepartmentGroup table. You can create additional containers for extra tables or create several packages. Then you will typically move these control tasks to a master package.

Changed- and deleted rows are handled in a batch using staging tables. These staging tables are created at the start of the container and dropped at the end.

The necessary BIML code to create the incremental load package
(available at GitHub Gist):

More Information:

1. MSDN: About Change Data Capture in SQL Server
2. Whitepaper by Paul Randal: Tracking Changes in your Enterprise Database
3. SQLCAT Article: Tuning the Performance of Change Data Capture in SQL Server 2008
4. mssqltips.com blog by Ray Barley: Process Change Data Capture in SQL Server Integration Services (2008)
5. Matt Mason: CDC in SSIS for SQL Server 2012

There are many reasons for me to blog. One of the less vain is to recover and reuse code I wrote earlier. In my current project we have a need to test, test and retest the initial load of the data warehouse.

For this purpose I wrote this T-SQL script that:

• Drops all foreign key constraints;
• Truncates all the tables;
• Recreates all foreign key constraints. I dropped earlier.
  

Some time ago a BIML enthusiast asked me for the location of the temporary files that BIDSHelper create when you generate the SSIS packages in BIDSHelper. I couldn't help him and explained that the Biml Engine first compiles the Biml documents,  applying any BimlScript in memory and then creates the SSIS packages. The intermediate step isn't persisted on disk.

Debugging Biml Files Made Easier

Obviously he needed this intermediate result to better debug his Biml files and improve his development efforts. Recently I learned this simple trick to create the intermediate results he wanted. And I like to share it with you in this blog post:

• Add a new Biml File to your project and name it SaveCompiledBiml.biml
• Replace the contents of this file with the next code block
  

Some remarks:

Change the directory and filename of the sFile variable to match your environment / wishes.
In this example I have used tier 5. If you have files with a higher tier change the template tier directive in the SaveCompiledBiml file.  
(BIML files are compiled in the order of their "tier", the files with the lowest tier first and those with the highest last. The default tier is 0 for files without BimlScript and 1 for files with BimlScript.)

Do you want to improve the quality and speed of your ETL-development?

Biml is quickly gaining popularity as the way to automate the creation of SSIS packages. And thus saving time and money while improving quality. Are you interested in automation of SSIS packages with Biml? Consider my Biml Workshop to get a headstart.

Some years ago the client of a contractor I worked for made some major investments in their IT-landscape. They replaced their ERP - and CRM system and of course BI/Reporting was part of the acceptance criteria for the new system. It was a big project and a disaster! ERP, CRM and BI consultants from the contractor where running in and out. Discussing requirement details with the client and adapting the systems to these wishes. For the BI team it was especially hard. When we build something on Monday chances were slim that it still worked on Thursday. We depended upon the ERP and CRM team to communicate their changes and provide us with correct test data. And there was no love wasted between the teams. I was very glad when the opportunity arose to leave this war hole and move on. And I did.

Trending

Nevertheless it seems to become a trend to build/adapt the BI system before a new source system has been launched. And make it part of the acceptance criteria for the new system. This of course offers the client an easy way to verify the new system by comparing the reports they work with. In my previous three projects (part) of the source system was still in development and I would probably have gone crazy keeping up with all the changes if I hadn’t been able to automate the work.

Agility is the name of the game

In these situations I have found that you (as in an agility drill) need three things:

• Light feet:
  An alert/reporting system that gives you the insights in the changes that are made in the source systems. I’ll typically import metadata of the source systems tables, views and columns in the database on a daily basis. See http://blog.in2bi.com/microsoft-business-intelligence/tsql-metadata-queries/ for example queries.
• Run on balls of feet:
  A data warehouse automation framework that automates the creation of the data warehouse objects (Tables, Views, Primary keys, Foreign key relations and Indexes) and the ETL procedures (Stored procedures and SSIS packages) to load the data into the data warehouse.
  I have written extensively about this earlier. See
  BIML:
  http://blog.in2bi.com/biml/creating-a-meta-data-driven-ssis-solution-with-biml-1-overview/
  http://blog.in2bi.com/biml/create-lightswitch-application-to-maintain-meta-data/
  DWH Deck:
  http://blog.dwhdeck.com/dwh-deck/
• Use Arms (to keep your balance):
  A testing framework that daily checks and alerts you about the results, compared to the results the business users expect.

Testing Framework

A testing framework has a complicated ring to it. But if you keep it simple and focus on the results the users expect to see it will be easy and the advantages are great:

• You’ll notice any errors early in the process.
• You can correct the errors before the users’ starts testing.
• You can pinpoint any changes made in the source system that ruin your reports.
• You’ll gain confident in your solution and sleep better.

I’ll describe a method that has worked for me. Key to success herein is starting early!

First get hard copies and digital versions of reports the users are using now. Ask them to highlight the important measures. Start entering the tests in an Excel spreadsheet and use the digital versions of the reports to copy any relevant data) I use the following format where I keep values in the column testName unique

Now the difficult/laborious part: start entering SQL statement in the expression column that will return the expected value. Use [criterion1] and/or [criterion2] as placeholders in these statements. The values in the criterion1 and criterion2 column will replace these placeholders at execution time. You will now be able to copy the expression to similar test with different values for the criteria. Example expression:

Testing Framework: Tables

Import your Excel spreadsheet into a SQL Server table with the following definition:

Create an additional table to store the result of the tests that were performed. Use the following definition:

Testing Framework: SSIS Package

Now create an SSIS Package that will perform the tests. It uses:

• An Execute SQL Task to get a list of tests
• A For Each Loop Container that is used to loop through the list with in it:
• An Execute SQL Task to execute every test
• An Execute SQL Task to log the result of every test

This package can be described with the following BIML (Business Intelligence Markup Language) snippet:

Conclusion

In this blog post I discussed the components of an agile system that are necessary when you build a data warehouse where the source systems are still in development:

• An Alert System to inform you of changes in the source systems.
• A Data Warehouse Automation Framework.
• A Testing Framework.

I ended with a simple implementation of a testing framework that worked for me. Does this help you or did you implement something similar? … I love to hear from you!

I wrote this blog post in august 2012, but somehow I forgot to post it. At the start of 2014 I wish every one many happy user peaks and wisdom in creating them…

Recently I have been involved in converting a business intelligence (dashboard) web application. Making it more suitable for tablets and other mobile devices. This offers a great opportunity to talk about this great image of Kathy Sierra:

Of course the location of the “Happy User Peak” will differ for every person. The message of the image however is very clear: limit options and features!

When constructing an application for mobile devices you’ll need to limit the features and options even further and make it really really simple for your users. They don’t want menus, toolbars, lookup textboxes, lists in combo boxes to choice from.

They just want to click and swipe to investigate the tables and charts presented in the dashboard.

As a consultant I often need to run a program as a different user. For future reference I collected the information about RunAs in this article.

In Windows 7 en Windows Server 2008R2 you can run an application as a different user  by holding down the shift key and right clicking the application shortcut.

To use this functionality in windows 8 you need some extra steps to configure it. These steps are described by Taylor Gibb in: How to Run Windows 8 Apps as a Different User from the Start Screen

Another option is to use the ShellRunAs utility that is provided by the Windows Sysinternals website. If you install this utility you can right-click on a shortcut and select “Start as different user”.

Runas Command

You can also use the runas command line tool from a command prompt or in a .bat file as in these examples:

%windir%\System32\runas.exe /netonly /user:domain\username "C:\Program Files\Microsoft SQL Server\110\Tools\Binn\VSShell\Common7\IDE\Ssms.exe”

This will prompt you for the password of “domain\user” and open Sql Server Management Studio. The \netonly parameter means that the provided identity will be used only with a remote resource the remote site will authenticate you as 'domain\username'.

As an alternative, first ask for the user name and use the input in the runas command:

set /P user="Type the domain\username: "
%windir%\System32\runas.exe /netonly /user:%user% "C:\Program Files\Microsoft SQL Server\110\Tools\Binn\VSShell\Common7\IDE\Ssms.exe”

Correct metadata is essential for every automation solution. When I started working with BIML I used one table that describes the source to target table mapping. (see the “Creating a Meta Data Driven SSIS Solution with BIML” series)

And that works fine in most simple scenarios like importing staging tables or when you are able to move business rules to a view. Key in these simple scenarios is that the columns in your target table have the same name and the same data type.

Extending the metadata model

In more recent assignments I added a column mapping table and used T-SQL to simplify the BIML script. With this approach I created more robust SSIS packages that provided extra possibilities, like:

• Incremental load patterns
• Converting data types
• Surrogate key lookups
• Expressions to calculate new values

A problem with this approach however is maintaining these column mappings. So I decided to take Visual Studio LightSwitch for a spin and create a simple application to fulfill my maintenance needs.

LightSwitch

Visual Studio LightSwitch is a rapid application development (RAD) tool that is used to help write data-centric line of business (LOB) applications. An import prerequisite of LightSwitch is that you need to have a data model or construct one using the LigthSwitch GUI. Based on this data model you can easily define a set of screens and your application is done. So: No coding necessary. (although coding is possible to extend the standard functionality)

Data Model

For my data model I decided to add two additional tables:

• ETLJob
• Connection

From a BIML perspective the ETLJob table is primarily used to create the master package with Execute Package and Execute SQL tasks.  An ETLJob can be either:

• A generated package (with one or more table mappings)
• A manual package or a
• SQL Statement

So I ended up with the following model:

The SQL DDL Statements to create this model:

CREATE SCHEMA meta
GO

CREATE TABLE meta.Connection
(
      ConnectionID INT IDENTITY NOT NULL PRIMARY KEY
    , ConnectionName VARCHAR(64) NOT NULL
    , ConnectionType VARCHAR(20) NOT NULL
    , ConnectionString VARCHAR(256) NOT NULL
    , CreateInProject BIT NOT NULL DEFAULT(0)
    , DelayValidation BIT NOT NULL DEFAULT(1)
)
CREATE TABLE meta.ETLJob
(
      ETLJobID INT IDENTITY NOT NULL PRIMARY KEY
    , ETLJobName VARCHAR(64) NOT NULL
    , ETLJobType VARCHAR(20) NOT NULL
    , ETLJobGroup VARCHAR(64)
    , SQLConnection INT
        REFERENCES meta.Connection(ConnectionID)
    , SQLStatement VARCHAR(512)
)
CREATE TABLE meta.TableMapping
(
      TableMappingID INT IDENTITY NOT NULL PRIMARY KEY
    , ETLJOB INT NOT NULL
        REFERENCES meta.ETLJob(ETLJobID)
    , TableName VARCHAR(64)
    , TableType VARCHAR(20)
    , TableConnection INT NOT NULL
        REFERENCES meta.Connection(ConnectionID)
    , TableSchema VARCHAR(64)
    , SourceConnection INT
        REFERENCES meta.Connection(ConnectionID)
    , SourceObject VARCHAR(256)
)
CREATE TABLE meta.ColumnMapping
(
      ColumnMappingID INT IDENTITY NOT NULL PRIMARY KEY
    , TableMapping INT NOT NULL
        REFERENCES meta.TableMapping(TableMappingID)
    , ColumnName VARCHAR(64) NOT NULL
    , ColumnType VARCHAR(20) NOT NULL
    , ColumnDataType VARCHAR(20) NOT NULL
    , SourceColumnName VARCHAR(64)
    , SourceColumnDataType VARCHAR(20)
    , Calculation VARCHAR(256)
    , LookupConnection INT 
        REFERENCES meta.Connection(ConnectionID)
    , LookupObject VARCHAR(256)
    , InputColumnName VARCHAR(64)
    , InputColumnDataType VARCHAR(20)
    , OutputColumnName VARCHAR(64)
)

Importing the data model in LightSwitch

To import this data model you only need 6 steps:

1. Create a new database. (I named it MetaBase) and execute the  afore mentioned DDL Statements to create the objects and relations.
2. In Visual Studio create a New Project. Select LightSwitch as template and choose LightSwitch Application (Visual C#). Give the project a name (I used Metabase) and click OK.
   
   
   
3. In the next screen click Attach to External Data Source.
   
   
   
4. In the Attach Data Source Wizard form select Database and click next.
   
   
5. In the Connection Properties window enter the server name\instance and Select the database you created in step 1. Click OK.
   
    
   
6. Check Tables and use the default name in Specify the name of the data source in the Choose your Database Objects step. Click Finish.
   
    
   

You have imported the data model into LightSwitch.

Changing the data model

When you look at the LightSwitch designer in your data model you will notice LightSwitch made some small name changes, describing the relations. Do not try to correct these. Instead change the display name in the properties window. As I did for the source connection in this screenshot.

Creating the screens

Creating screens is even easier than creating the data model.

1. Right-Click Screens in Solution Explorer and choose Add Screen ..
   
   
   
   
2. In the Add New Screen dialog select Details Screen as template. Select MetaBaseData.ETLJob as Screen Data and check ETLJob TableMapping. Click OK.
   
   
   
   
3. After I created the screen I made some small changes in the designer: Moved some fields up or down by dragging and dropping and changed the number of Lines in the SQL Statement field from 1 to 3.
   
   
   
   

I repeated steps 1 and 2 to create additional screens:

1) Add ColumnMappings under Additional data to include
2) Add TableMappings under Additional data to include

Navigation, Shell and Theme

Right-Click Screens en select Edit Screen navigation from the context menu. Change the screen navigation to the following image:

Choose General Properties and change the Shell to LightSwitch Standard Shell and the Theme to LightSwitch Blue Theme.

Conclusion

With Visual Studio LightSwitch you can easily create an application to maintain the meta data for your BIML solution. You create a normalized data model. Import it in LightSwitch and start adding screens. And if you like BIML you’ll probably like LightSwitch as well: Both make it easier to program your solution.

An additional advantage of storing the meta data in separate tables and creating an application to maintain that data is that you have a great overview of your data lineage and up to date documentation. Here are some screenshots of the application with data.

^{Search ETLJob screen showing the packages and SQL Statements of our solution.}

^{An ETL Job detail screen with the associated table mappings.}

^{A Table Mapping detail screen with the associated column mappings.}

The combination of XML and C# code in a Biml file can make Biml files very complex. In web development Microsoft overcame this problem by introducing the code-behind model with one file for the static (html) text and a separate file for the dynamic code. Unfortunately this is not possible with Biml. There are however some ways to make your files less complex:

1. Separate files
2. Move code logic to T-SQL

In this post I’ll briefly describe the first option and use some examples to explain the second option.

Separate files

You can use the include directive to insert a piece of static xml of another file in your Biml file. John Minkjan has a nice example on his website.
If you need more dynamic content you can also opt for the CallBimlScript function which will allow you to use properties. Of course you will have to handle these properties in the callee file.

Move some code logic to T-SQL

A typical Biml solution exists not only of Biml files but also of metadata that describe the packages that you want to build. I typically use a table mapping table and a column mapping table in a SQL Server database. This allows me to create a stored procedure that combines information from both tables in one dataset with all relevant information in one row.

For the next examples I will use the following information in this source to target mapping table:

Using FOR XML PATH(‘’) in T-SQL

With the “FOR XML PATH(‘’)” syntax you can transform columns into a string. The T-SQL statement:

SELECT srcColumnList = SELECT  ', ' + srcColumn 
FROM meta.ColumnMapping WHERE srcColumn is not null
FOR XML PATH ('')

returns: , Id, f_name, l_name, sex a string you can almost use as a column list in a source component in the SELECT <column list> FROM <source table> statement. Almost … because you’ll have to remove the first comma and handle strange characters in column names. So you’ll have to do some stuff to remove this comma:

SELECT srcColumnList = STUFF((SELECT  ', ' + QUOTENAME(srcColumn) FROM meta.ColumnMapping WHERE srcColumn is not null
FOR XML PATH('')),1,2,'')

which returns the string we need: [Id], [f_name], [l_name], [sex]

Creating the data conversion task

Expanding on the previous statement you can create additional dynamic content for your Biml solution. In this case the column definition in  a Data Conversion Task. In Biml you would write:

<DataConversion Name="DC">
  <Columns>
    <Column SourceColumn="f_name" TargetColumn="FirstName"
            DataType="AnsiString" Length="40" CodePage="1252" />
     <…more columns …>
</Columns>
</DataConversion>

To create the column list for this data conversion use the statement:

SELECT DCColumns = REPLACE(REPLACE(STUFF(
    (SELECT  char(10) + '<Column SourceColumn="' + srcColumn 
        + '" TargetColumn="' + tgtColumn
        + '" DataType="' + tgtDataType
        + CASE WHEN tgtDataType='AnsiString'
        THEN '" Length="' + CAST(tgtLength AS varchar(10))
             + '" CodePage="1252" />'
        ELSE '" />' END
     FROM meta.ColumnMapping
     FOR XML PATH('')),1,1,''),'&lt;','<'),'&gt;','>')

Which returns the Biml string we need:

<Column SourceColumn="Id" TargetColumn="CustomerID"
     DataType="Int32" />
<Column SourceColumn="f_name" TargetColumn="FirstName"
     DataType="AnsiString" Length="40" CodePage="1252" />
<Column SourceColumn="l_name" TargetColumn="LastName"
     DataType="AnsiString" Length="40" CodePage="1252" />
<Column SourceColumn="sex" TargetColumn="Gender"
    DataType="AnsiString" Length="6" CodePage="1252" />

Some remarks to the SQL statement:

• We don’t really need the char(10), but the line break is convenient when we look at the results.
• Since this query uses the for xml syntax and xml can’t handle the opening en closing tag signs. SQL server replaces them with their escape codes. We have to use the REPLACE function to change these escape codes back into the opening and closing tag signs.

Creating the stored procedure

For this example I would create the following stored procedures that combines the two metadata tables:

CREATE PROCEDURE meta.getPackageDetails (@MappingType varchar(50)) AS
SELECT
      PackageName = t.MappingName
    , TargetTable = t.tgtSchema + '.' + t.tgtTable
    , TargetConnection = t.tgtConnection
    , SourceTable = t.srcSchema + '.' + t.srcTable
    , SourceConnection = t.srcConnection
    , srcColumnList = STUFF((SELECT  ', ' + QUOTENAME(srcColumn)
        FROM meta.ColumnMapping
        WHERE srcColumn is not null
        AND TableMappingID=t.TableMappingID
        FOR XML PATH('')),1,2,'')
    , DCColumns = REPLACE(REPLACE(STUFF(
        (SELECT  char(10) + '<Column SourceColumn="' + srcColumn
        + '" TargetColumn="' + tgtColumn
        + '" DataType="' + tgtDataType
        + CASE WHEN tgtDataType='AnsiString'
        THEN '" Length="' + CAST(tgtLength AS varchar(10))
            + '" CodePage="1252" />'
        ELSE '" />' END
        FROM meta.ColumnMapping
        WHERE TableMappingID=t.TableMappingID
        FOR XML PATH('')),1,1,''),'&lt;','<'),'&gt;','>')
FROM meta.TableMapping t
WHERE t.MappingType = @MappingType

Less complex Biml file

The Biml file that you need to create the packages:

<Biml xmlns="http://schemas.varigence.com/biml.xsd">
  <#@ include file="Connection.biml" #>

    <Packages>
    <# string sConn =  “Provider=SQLNCLI10;Server=.\\SQL2012;
       Initial Catalog=BimlSamples;Integrated Security=SSPI;"; #>
    <# string sSQL = string.Format("Exec meta.getPackageDetails
      {0}", "dim"); #>
    <# DataTable tblPackages = ExternalDataAccess.GetDataTable
      (sConn,sSQL); #>
    <# foreach (DataRow pkg in tblPackages.Rows){ #>
       
        <Package Name="<#=pkg["PackageName"]#>"
                ConstraintMode="Linear">
            <Tasks>

        <Dataflow Name="DFT <#=pkg["PackageName"]#>">
          <Transformations>
            <OleDbSource Name="ODS Source"
              ConnectionName="<#=pkg["SourceConnection"]#>" >
              <DirectInput>
                SELECT <#=pkg["srcColumnList"]#>
                FROM <#=pkg["SourceTable"]#>
              </DirectInput>
            </OleDbSource>
           
            <DataConversion Name="DC">
              <Columns>
                <#=pkg["DCColumns"]#>
              </Columns>
            </DataConversion>

            <OleDbDestination Name="ODD Target"
                ConnectionName="<#=pkg["TargetConnection"]#>">
              <ExternalTableOutput
                 Table="<#=pkg["TargetTable"]#>"/>
            </OleDbDestination>

          </Transformations>
        </Dataflow>
      </Tasks>
        </Package>
        <#}#>
    </Packages>
</Biml>
<#@ import namespace="System.Data" #>

Conclusion

In this blog post I discussed some ways to make you Biml files less complex. You can move (semi)-static content to other files and import them with the include directive or use the CallBimlScript function. And you can move parts of complicated Biml code to T-SQL. The choice of how much you will move to T-SQL will largely depend on your proficiency in C# or T-SQL.

You can leverage Business Intelligence Markup Language – or BIML – to automate the creation of Microsoft SQL Server Integration Services (SSIS) Packages. The popular open source BIDSHelper project includes Biml functionality, enabling anyone to write and execute BIML code for free. Among professional SSIS Developers BIML is quickly gaining popularity.
In this post I’ll share some practical tips ….

1. Better copy and paste experience

The irritating behavior of the XML editor in Visual Studio when copying BIML script and how to overcome it  has been documented on several blogs. In this overview of tips I couldn’t discard it.
In Visual Studio / SSDT … Select Options in the Tools menu.
In the Treeview of the Options form expand Text Editor, expand  XML and choose Formatting.
Next uncheck both options under Auto Reformat.

2. Put directive tags #@..# at the bottom of your BIML file

In many examples (including mine) these directive are placed at the top of the BIML file. Which makes sense because this is the default location in software development. However when Visual Studio opens a file with a directive before the <Biml> xml tag it doesn’t use the xml editor and we lose the formatting and intellisense features in the gui.
So instead place the directives at the bottom of the file. After the closing </Biml> tag. This will not have any effect on the creation of packages.

3. Vanilla Biml file

Before using script in a BIML file create a working BIML file that can create a package with more than 80% of the expected functionality.
Copy this file and use it as a base and then start scripting.
Why? The Combination of xml and code in one document makes it more complicated to select the correct BIML elements and attributes. Next use a small dataset so when you test your work only a small amount of packages are created.

4. Test and save often

During development regularly often check your work. Use the options: “Check Biml for Errors” or “Generate SSIS Packages” from the context menu. This way you not only test your work but save it as well.
Why? Debugging BIML files is mostly a pain. Error messages are limited and often refer to the wrong row and small typos can have a huge impact. So you better find your errors early in development.

5. Special XML characters

Xml has some special characters that you need to enclose in  a CDATA tag or replace the special character with its escape code:

• double quote " ( &quot; )
• single quote '  ( &apos; )
• less than sign  < ( &lt; )
• greater than sign  >  ( &gt; )
• ampersand & ( &amp; )

As an example suppose you have the following BIML:

<Direct Input>
SELECT Name FROM dbo.People WHERE Age > 25
</Direct Input>

then the xml processor will fail at Age > 25 As a remedy change your BIML into:

<Direct Input>
<![CDATA[SELECT Name FROM dbo.People WHERE Age > 25]]>
</Direct Input>, or

<Direct Input>
SELECT Name FROM dbo.People WHERE Age &gt; 25
</Direct Input>

6. Special C# characters

C# also as some special characters that you will need to escape with a backslash . Most notably:

• the backslash itself \ ( \\ )
• single quote ‘ ( \’ )
• double quote “ ( \” )

As an example escaping the backslash in a file location  
string FileName = “C:\\Dir\\File.txt”;
or use the verbatim string construction:
string FileName = @”C:\Dir\File.txt”;

7. Learn some basic C#

C# is the principal language of the .NET framework and is widely used for all sorts of programs: Web Services, Web Applications, Windows Form applications, SSIS Scripts, SQL CLR Stored Procedures etc. An investment in learning some C# will pay off. There is an abundant supply of websites and books with relevant information.

To get you started: read the chapters Basics  and  Flow control  off This tutorial: http://zetcode.com/lang/csharp/

8. Learn from the samples

Steal / use the samples on:

• Varigence samples http://varigence.com/Documentation/Samples/Biml
• BimlScipt.com
  http://bimlscript.com/
• My blog posts on BIML
  http://blog.in2bi.com/biml/
• Andy Leonard’s Stairway to Biml on SQLServerCentral
  (sign up mandatory)
  http://www.sqlservercentral.com/stairway/100550/
• The series John Welch  wrote on the BIML functionality in BIDS Helper
  http://agilebi.com/jwelch/2011/05/13/biml-functionality-in-bids-helper/
• The blog of John MinkJan on BIML
  http://biml101.blogspot.nl/

This is the second post of a diptych on the magical windowing functions in data warehouse scenarios. With these functions you can greatly simplify the TSQL you write. Many complex queries with CTE’s, temp tables and sub queries can be rewritten to simpler, better maintainable and better performing queries.  In this post I’ll dive into some possibilities for reporting.

For the examples in this post I’ll use the Contoso Retail Data Warehouse database. A sample database for data warehouses provided by Microsoft.

Year To Date (YTD) Calculations

On the Internet you’ll find a lot of examples on using the running total technique to calculate year to date values. In this example I need the monthly sales and the YTD sales for every store.

SELECT CalendarMonth
  , StoreName
  , PeriodSales
  , SalesYTD = SUM(PeriodSales) OVER 
     (PARTITION BY StoreName, CalendarYear ORDER BY CalendarMonth) FROM
  (
  SELECT CalendarYear
    , CalendarMonth
    , StoreName
    , PeriodSales = SUM(sal.SalesAmount)
  FROM FactSales sal
  JOIN DimDate dat ON sal.DateKey = dat.Datekey
  JOIN DimStore sto ON sal.StoreKey = sto.StoreKey
  GROUP BY CalendarYear, CalendarMonth, StoreName
  ) SalesByMonth
ORDER BY StoreName, CalendarMonth

The sub query “SalesByMonth” aggregates the sales amount for every store per month. The windowing function SUM() OVER() calculates the YTD sales. Which will result in the required dataset:

The SUM(SUM()) OVER() Construction

Since you can use Windowing Functions over an aggregated we don’t need the sub query and we can simplify this query to:

SELECT CalendarMonth
  , StoreName
  , PeriodSales = SUM(SalesAmount)
  , SalesYTD = SUM(SUM(SalesAmount)) OVER 
     (PARTITION BY StoreName, CalendarYear ORDER BY CalendarMonth) FROM FactSales sal
JOIN DimDate dat ON sal.DateKey = dat.Datekey
JOIN DimStore sto ON sal.StoreKey = sto.StoreKey
GROUP BY CalendarYear, CalendarMonth, StoreName
ORDER BY StoreName, CalendarMonth

The second SUM in: “SUM(SUM()) OVER() GROUP BY “ is used in conjunction with the GROUP BY clause to calculate the monthly sales first.
The first SUM in: “SUM(SUM()) OVER() GROUP BY “ is then used in conjunction with the OVER clause to calculate the YTD sales.

Comparing to previous year

Adding the figures of the previous year as a comparison is a common reporting requirement. You can easily realize this by using the LAG function returning the results 12 months back in time. Building upon our earlier query:

SELECT *
  , PeriodSalesPrevYear = LAG(PeriodSales,12,0)
      OVER (PARTITION BY StoreName ORDER BY CalendarMonth)
  , YTDSalesPrevYear = LAG(SalesYTD,12,0)
      OVER (PARTITION BY StoreName ORDER BY CalendarMonth)
FROM
(
  SELECT CalendarMonth
    , StoreName
    , PeriodSales = SUM(SalesAmount)
    , SalesYTD = SUM(SUM(SalesAmount))
        OVER (PARTITION BY StoreName, CalendarYear ORDER BY CalendarMonth)
  FROM FactSales sal
  JOIN DimDate dat ON sal.DateKey = dat.Datekey
  JOIN DimStore sto ON sal.StoreKey = sto.StoreKey
  GROUP BY CalendarYear, CalendarMonth, StoreName
) Base
ORDER BY StoreName, CalendarMonth

Which results into:

How Do We Do Compared to the other stores?

In this example I use the RANK() Function to determine the store’s rank in the total monthly sales and the store’s sales as a percentage of the total monthly sales:

SELECT CalendarMonth
  , StoreName
  , PeriodSales = SUM(SalesAmount)
  , StoreRank = RANK() OVER
      (PARTITION BY CalendarMonth ORDER BY SUM(SalesAmount) DESC)
  , StoreShare = 100*SUM(SalesAmount)/
      SUM(SUM(SalesAmount)) OVER (PARTITION BY CalendarMonth)
FROM FactSales sal
JOIN DimDate dat ON sal.DateKey = dat.Datekey
JOIN DimStore sto ON sal.StoreKey = sto.StoreKey
GROUP BY CalendarMonth, StoreName

Compare to (Average of) Previous Periods

In a recent client engagement a report which was used to audit the monthly invoice process gave a lot of troubles. The SQL query behind it was very difficult to comprehend and consisted of several sub queries. By using windowing functions our team was able to greatly simplify the query. The requirement can be restated/simplified to our example as: Give us the current month sales, the previous 3 and the average of those previous 3. This is the resulting query:

SELECT CalendarMonth
  , StoreName
  , PeriodSales = SUM(SalesAmount)
  , SalesPrevPeriod1 = LAG(SUM(SalesAmount),1,0)
      OVER (PARTITION BY StoreName ORDER BY CalendarMonth)
  , SalesPrevPeriod2 = LAG(SUM(SalesAmount),2,0)
      OVER (PARTITION BY StoreName ORDER BY CalendarMonth)
  , SalesPrevPeriod3 = LAG(SUM(SalesAmount),3,0)
      OVER (PARTITION BY StoreName ORDER BY CalendarMonth)
  , AveragePrevPeriods = AVG(SUM(SalesAmount))
      OVER (PARTITION BY StoreName ORDER BY CalendarMonth
      ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING)
FROM FactSales sal
JOIN DimDate dat ON sal.DateKey = dat.Datekey
JOIN DimStore sto ON sal.StoreKey = sto.StoreKey
GROUP BY CalendarYear, CalendarMonth, StoreName
ORDER BY StoreName, CalendarMonth

I especially like the way you can use the window frame clause to limit the average to 3 periods: ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING

More Information:

My previous post on using Windowing Functions focused on dimensions 

MSDN (Books on Line) about the OVER Clause

Introduction blog series on Windowing Functions by Fabiano Amorim on simple talk

Blog post with a instructional video on the SQL 2012 Windowing Functions Leaving the Windows Open by Jeremiah Peschka

Book: Microsoft® SQL Server® 2012 High-Performance T-SQL Using Window Functions by Itzik Ben-Gan