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Thread: Left outer Join in Mondrian Schema?

  1. #1
    Join Date
    Apr 2013
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    19

    Default Left outer Join in Mondrian Schema?

    I'm trying to create a new Mondrian schema... however, when I do it always defaults my dimension to an inner join. I'm looking for a left outer join with my fact table as my left table and dimension as my right.
    I need to be able to see all the values on my fact table even though they are not on my dimension table.... is that possible?

  2. #2
    Join Date
    Jan 2013
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    551

    Default

    Short answer is Mondrian always uses inner joins.
    Is there a reason you have rows in your fact table without corresponding values in your dimension table? If that's not something you can change in the physical tables, you could potentially create a view (either dbms or Mondrian <View>) and use coalesce to convert null values in the fact table to a key which you can link to a [Missing] member in the dimension table.

  3. #3
    Join Date
    Apr 2013
    Posts
    19

    Default

    I was hoping you wouldn't say that!!

    The main reason why I would I have null values in there is because I am bringing data from all different data sources into one DB. In some cases, there are rows in my dimension table that do not have the proper key to connect to that fact table, I want to identify those and fix those rows.

    Like you said and what I wanted to avoid, I'm going to have to just create an ID on both tables that will do the trick.

    Is there any specific reason to why Mondrian cannot do left joins?

  4. #4
    Join Date
    Jan 2013
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    551

    Default

    No reason in principal. Outer joins in data warehouses are less common.

    I know some others have requested it (MONDRIAN-1331), so this may be an area of work in the future.

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