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Hi All,
What are circular references and how to avoid them
Anand
One thing to remember is that QlikView compresses data so you don't have to worry about duplicate values or load the same table twice!
Remembering this is not relevant - let us load the data once and let it be compressed anyway, how does compression is related to this issue? i didn't get it!
So you can load the same table twice to avoid circular reference? It's very trivial. First load the data from SQL and store it into QVD. Then load country data from thsi QVD twice.
edit:
QVD load is very fast. So in a way you are loading data only once from SQL to QVD.
Handling loops in datawarehouses is not as straightforward as you might think. Some OLAP tools create Cartesian products between all possible combinations of dimensions, resolving different subqueries for each combination. Although the simplicity of the datamodel seems appealing, you wont like the drop in performance and issues it brings (ambiguity in query construction).
So I can understand why Qlik chose to restrict loops, and as a consequence, I don't think it's possible to use a single country table the way you intended. On the bright side, the design modifications arnt that difficult. The only argument I can think of in favor of having one table, is if you want a single select field COUNTRY, and all data on the sheet to correspond to that. You can use field triggers to align home country and car manufacturing country to resolve that.
I dont want all the data on the sheet to correspond to a single select field COUNTRY.
I want to have multiple COUNTRY fields (e.g Home COUNTRY & Carmaker COUNTRY) but to load the COUNTRY table once, and link it twice.
What are you trying to accomplish by linking twice to the same table?
Hi its.anandrjs:
Reloading complex, weirdly related and large amount of data, which means, creating the associative model, becomes more than once an art.
Since theory is practicably impracticable, please send us an example and your model will be tight satisfactorily by any one of the hundreds of bright brains in this flourish community.
The data is not "Wierdly related" - see page 146 in the manual - i want to see the sales of French cars by people who live in Canda - this is it, simply stated - what is the design practice for loading the countries once, and link it twice?