Steve Dark at Quik Intelligence has published a blog posting on Perfecting Your Qlikview Data Model. Steve reminds us that Qlikview table associations are very difference from associative data model joins — read on:
Getting your data model correct is critical to any QlikView development. This article gives advice on how you should approach this task and all the things you should consider…
Careful consideration also has to be given to the fact that QlikView associations work in a very different way to SQL joins. As you probably already know; any fields with the same name in more than one table will associate. If there are more than one field with the same name a synthetic key is created – and this is always a ‘bad thing’. If you see extra tables in your data model with a dollar sign in the name you need to revise and improve your model.
In my experience it is almost always better to concatenate fact tables together rather than to try and join them. This way you can have many columns with the same name and the values in them will appear just as one field in QlikView. Selecting a value in that field will pull out values from each of the concatenated tables. This technique is especially useful when pulling data from different sources, or applying budget or forecast data into your model. Concatenation is ideally done by having exactly the same fields in all tables you wish to concatenate (concatenation will then happen automatically) or by forcing a concatenation with a CONCATENATE statement. If using the latter method make sure you are aware of the impact on Optimized QVD Loads.
See on www.quickintelligence.co.uk