SQL Saturday #226 in South Florida, USA

I am excited yet again as I will be speaking at SQL Saturday #226 in sunny South Florida, USA. I will be speaking in the BI and Reporting Track in the afternoon. If you are from the South Florida region, please don’t miss out on this exclusive training day on everything SQL Server.

The event schedule is listed here.



Update: I had a great time speaking at Fort Lauderdale, Florida. Below is a farewell photo with other speakers (happy faces)

SQL Saturday South Florida Speakers

Speaking at SQL Saturday #224 – Sydney 2013

I am excited about speaking in my residential city of Sydney for SQL Saturday #224 on 25 May, 2013. I am extending the presentation I did for SQL Saturday #210 in Brisbane last month (Agile BI with SQL Server 2012 and TFS 2012). I am looking forward to seeing my mates from the Sydney BI community.


Please register if you haven’t done already.

The event will be held at:

Epping Boys High School (EBHS),
213 Vimiera Road
Eastwood, NSW, 2122

The schedule for the day is put up here.

Statistical Median with T-SQL (2012)

I have been interacting with my statistician colleagues lately and there was a reporting requirement to calculate medians over a spread of continuously distributed values. Thankfully with SQL Server 2012, you do not have to use the ROW_NUMBER() function as you had to with earlier T-SQL versions.

PERCENTILE_CONT and PERCENTILE_DISC are now available in T-SQL 2012. According to the SQL BOL, these functions are described as:

PERCENTILE_CONT: Calculates a percentile based on a continuous distribution of the column value in SQL Server 2012. The result is interpolated and might not be equal to any of the specific values in the column.

PERCENTILE_DISC: Computes a specific percentile for sorted values in an entire rowset or within distinct partitions of a rowset in SQL Server 2012. PERCENTILE_DISC calculates the percentile based on a discrete distribution of the column values; the result is equal to a specific value in the column.

Let us put these functions to test and understand them a bit more in detail:

I have a sample table(ServiceCost) with ServiceIDs (that will be the data element to group by) and Cost (the field for which medians have to be calculated).


I calculated the medians using PERCENTILE_CONT and PERCENTILE_DISC as below:




              OVER (PARTITION BY ServiceID) AS MedianValue,


              OVER (PARTITION BY ServiceID) AS MedianDisc

  FROM ServiceCost

  order by ServiceID<code>


The result of this query is:


The difference between the way these two functions work is clear from the output for ServiceID: SA456. The PERCENTILE_CONT function calculated the mean of the values {62,73} to result in 67.5; while the PERCENTILE_DISC function resulted in the value 62 which is one of the column values in the data set.

We can now show off the power of T-SQL for statistical analysis… Hurray!

SSIS Script Task – Upgrade to SSIS 2012

I upgraded a set of SSIS packages from SSIS 2008 R2 to SSIS 2012 and all of them had a smooth upgrade except for one. I had script tasks in almost all the packages which ran succesfully after I upgraded and tweaked them.

There was one package which was giving me trouble and functionally it dealt with moving, loading and deleting files from various folders. I upgraded the script task, updated all references, modified the project paramaters (as I am using the Project Deployment Model) and when I tried to run the package (Debug mode), the following generic error popped up:

Exception has been thrown by the target of an invocation.
at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
at Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTATaskScriptingEngine.ExecuteScript()


This error message was very generic and did not help me in tracking down the root cause. I decided to put a breakpoint into the Main() method of my script and tried debugging the package again. I was surprised when the script task opened up in VSTA and reached my breakpoint (which contradicted the generic error message – Invocation Error). The issue was with folder security to access the files.

Hope this helps fellow ETL developers who might come across similar issues with a generic invocation error.

SSRS KPI Indicators for non-numerical values

Today, I would like to share a quick and easy solution to display Traffic-Lights indicator for statuses in a workflow process. I recently implemented a workflow-driven report using SSRS which allows users to mark the receipt of documents and to further update the status of documents as “Signed Off”, “Submitted” etc. The requirement was purely to provide a workflow-driven report to the users. I took advantage of SSRS’ native KPI indicators to include a traffic-lights indicator to show the status graphically as it changes. This proved to be a quick win for my client users.

To start with, I designed the following report with link buttons for users to update the status. These links point to the same report with a dataset calling a stored procedure to update the status. Since this post focusses on the indicators, I shall stick to doing just that.


I have an record for a given document and it is marked as “Received” by default. (Notice the yellow colour traffic light indicator). The user can change the status to “Current” which then turns the colour of the indicator to green as shown below.


Lets take a closer look at the settings to achieve this.

Right click on the report body and select Indicator from the list of available report items.


From the available Indicator types, select the “rimmed traffic lights indicator” and place it on the report. After resizing and adjusting the position of the indicator, right click on the indicator and select Indicator Properties.


In the Indicator Properties dialog, select the Values and Scales tab and notice the preset numerical values for each colour. These range values can be modified to ranges that suit your needs. As discussed earlier, my requirement was to change the colour depending on a string field value which holds the status as “Received“, “Current”, “Submitted” or “Cancelled“. The value expression comes in handy to set numerical values to each of the string statuses.

I assigned a numerical value to each of the string values in my status field. The indicator then uses the corresponsing numerical value to change the colour based on the defined range.

From the expression above, if the status is set to “Cancelled” a zero value is returned which falls in red colour’s range. Thus, the report then displays the red coloured indicator. While this is a simple solution to use non-numerical KPIs to display indicators on your report, more advanced indicators can be implemented along the same lines.