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This document concerns data modelling and joins
See also my blog post on the same subject: To Join or not to Join.
Excellent as usual
Fabrice
Excellent Job Done... Very Useful.
Muy bueno.
Gracias
Simple And Clear
great job !
Thank you very much
Hi
1. I made two inline tables just to test the keep function. Left and inner keep works fine, but a pure keep does not work?
2. I am very confused, I thought that star schemes where recommended with Qlikview, but here normalization is recommended in most cases?
3. What happens in a join if only some of the data in the specific rows are the same?
1. If you don't specify which type of Join, then it is "Outer". The same logic applies for Keep, but since "Outer Keep" doesn't make sense....
2. It is a trade-off. Snowflake scheme is in my opinion easiest to maintain and should therefore be used. But for large data sets, a star scheme outperforms the snowflake scheme. So, star scheme may then be the better option.
3. Depends on whether you use Outer, Left, Right or Inner Join.
HIC
thx:
1. ah okay, of course it does not makes sense then Since it accept "keep" as single word in the code, marked as blue, I thought it would do something. So I guess it only evaluates single words.
2. I thought normalization was for large data set and complex systems. Does the star and snowflake only make sense with a fact/dimensional approach?
3. I will do some more testing
very informative - thanks for sharing