Why many cardinality combinations for each type of join in cognos

[nsaxena]

Hi All ,
I have worked on database and have understanding of joins there.

Example : for inner join we use join table a ,table b on maching columns.

But in cognos how to define inner join :- i could see many options,hence got confused as in database inner joins is through only one syntax,but in cognos i could see different cardinality selection for same.
Example : table a(1:1) table b (1:1) is also inner join i saw,and table a(1:n) table b (1:n) is also join.
What is difference.Can some explain me with small example.

Also for outer join i could see many combinations like :- 0..1<-->0..1 ,0..n<-->0..n

What is difference in all above case

Similarly for left outer join it is : table a( 0..n) and table b(1..n) > Left outer in table a.

I am confused that why we have so many combinations for each type of join and what is difference in each type of combination,as when compared to sql,we define in one shot each join.
Kindly help me in understanding this in cognos.

Many thanks in advance!!

[Lynn]

Your question is around a very important aspect of framework manager modeling. Below is one link that will help, but you would do best to invest in some professional training if you intend to do FM modeling. You should also read the user guide thoroughly as many topics are covered well in there.

Cardinality has a lot to do with the identification of facts vs dimensions and impacts how SQL will be generated from your model.

http://www-01.ibm.com/support/knowledgecenter/SSWGNW_10.1.0/com.ibm.swg.im.cognos.ug_fm.10.1.0.doc/ug_fm_id4278cardinality.html%23cardinality

[nsaxena]

Hi Lynn

Document link was helpful. Thanks!