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IBM Cognos 10 Platform => Cognos 10 BI => Framework Manager => Topic started by: BenziD on 07 Jan 2013 07:17:04 AM

Title: what is the difference between 1...N or 1...1 relation?
Post by: BenziD on 07 Jan 2013 07:17:04 AM
when i have two tables (A,B), creating join between them (A.a = B.b)
the generated SQL will be A.a = B.b
Title: Re: what is the difference between 1...N or 1...1 relation?
Post by: MFGF on 07 Jan 2013 07:39:07 AM
The query engine uses the cardinality to figure out how to construct queries. It assumes your structures are star schema (or snowflake schema) tables, and determines fact from dimension as follows:

If a query subject is at the 'n' end of *all* relationships used in the query, it is identified as a Fact
If a query subject is at the '1' end of any relationship used in the query, it is identified as a Dimension

This is why you should model as star schemas in FM, even if the underlying tables are normalized.

Cheers!

MF.