At the Masters Summit for QlikView in London we ended the second day with an informal ‘stump the geek’ session. In this session participants could submit technically challenging questions to a panel. Besides the four presenters, this panel also consisted of Steve Dark, Stephen Redmond and Henric Cronström. You can imagine that I found myself surrounded by an awesome amount of QlikView knowledge.
While challenging, most of the questions could either be answered on the spot or a conceptual solution could be described. There was however one question that didn’t really yield an, in my opinion, satisfactory answer. The consensus almost seemed to drift towards ‘it cannot be done’ or ‘that is not how QlikView works’. The question was:
Can we make “or” selections between list boxes, instead of the standard “and” selections?
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September 21, 2011 – 12:30
Today I will show you how to store variables and their definitions in an external file… and why you would want to do that.
To start with the last part, in my opinion it is important to apply calculations and business rules consistently across QlikView applications. Doing this manually takes a lot of time and is prone to errors. Besides that, it is just not a very fun task. Fortunately, a lot of this can be handled by setting up a multi tiered environment with one or more QVD layers (for more information on this, see Rob Wunderlich’s excellent “Understanding & Best Practices with QVD files” webinar and slides).
Sometimes however, you need to use calculations that cannot be (easily) pushed to a QVD layer, for example when calculating averages or using set analysis. How can you store those calculations in a central place so they can be reused?
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After my previous post about variables, I got an interesting question from DV. He asked me about the reuse of chart expressions by referencing the label of another expression (“label referencing”), and what the performance implications of using variables and label referencing versus direct expressions are.
I use variables and label referencing extensively in my applications, but I never really tested what this means for performance. I have always assumed that using variables instead of direct expressions would have a slight impact on performance. I also suspected that using label referencing would result in significantly better performance (I will explain this later).
But was this really true? Triggered by DV’s question, I set up a small experiment to test my assumptions.
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