Forum Discussion
Issues with filter propagation
What you are describing here is the concept of expanded tables which is basically that the table on the one side of a many to one relationship, includes all the columns from the many side. So in your example, the entire Sales table are its' columns + all columns from the Product table.
When you filter the Product table by the entire Sales table, the resulting table is that of products which have been sold. Which is why you get the same amount of rows in the products table that are in the sales table. But that only works when you use an entire table as a filter ( and remember filters are tables...), and entire table is the tables actual columns you see plus all the ones that are on the many side. And you are corret, this does make it appear that filter flow up-hill. Which they do not, but sure seems like it.
That is quick explanation of what is happening here and really does require some more in-depth understanding of the theory to really get what is going on here. Not sure what books you have but if this is the type of thing you are wanting/needing to understand, I'd suggest picking up the Definitive Guide to Dax for sure.
What you are describing here is the concept of expanded tables which is basically that the table on the one side of a many to one relationship, includes all the columns from the many side. So in your example, the entire Sales table are its' columns + all columns from the Product table.
When you filter the Product table by the entire Sales table, the resulting table is that of products which have been sold. Which is why you get the same amount of rows in the products table that are in the sales table. But that only works when you use an entire table as a filter ( and remember filters are tables...), and entire table is the tables actual columns you see plus all the ones that are on the many side. And you are corret, this does make it appear that filter flow up-hill. Which they do not, but sure seems like it.
That is quick explanation of what is happening here and really does require some more in-depth understanding of the theory to really get what is going on here. Not sure what books you have but if this is the type of thing you are wanting/needing to understand, I'd suggest picking up the Definitive Guide to Dax for sure.
Anonymous
Cool. Thanks a lot Nick.
I am actually a few pages away from the subchapter that describes expanded tables in the Definitive guide to DAX. I'll read it and see what I can make of it. I might get back to you with some questions :smileyhappy:
Thanks so much for pointing me in the right direction. This had been bothering me for some time now.
No problem at all. It's not an overly complex subject, it can just be alot to remember. I reference that book quite a bit. Good luck :)
For those with no access to the book, here's a interesting article on the topic by the same authors:
