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Saturday, 16 February 2013

Cardinalities in Cognos frameworkHi Guys,

Below is note on cardinalities .I have taken the content from IBM cognos helpguide .You can findthe same in cognos framework userguide .Just noting down point for my reference .

taken from IBM

IBM helpguide Link

IBM Cognos 8 supports both minimum-maximum cardinality and optional cardinality.

In 0:1, 0 is the minimum cardinality, 1 is the maximum cardinality.

In 1:n , 1 is the minimum cardinality, n is the maximum cardinality.

A relationship with cardinality specified as 1:1 to 1:n is commonly referred toas 1 to n when focusing on the maximum cardinalities.

Note --- so 0:1 to 1:n is also read as 1 to n

A minimum cardinality of 0 indicates that the relationship is optional. You specify a

Cardinality in Generated Queries

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minimum cardinality of 0 if you want the query to retain the information on the otherside of the relationship in the absence of a match. For example, a relationshipbetween customer and actual sales may be specified as1:1 to 0:n. This indicatesthat reports will show the requested customer information even though there maynot be any sales data present.

Therefore a 1 to n relationship can also be specified as:

0:1 to 0:n

0:1 to 1:n

1:1 to 0:n

1:1 to 1:n

Use the Relationship impact statement in the Relationship Definition dialog boxto help you understand cardinality. For example, Sales Staff (1:1) is joined to Orders(0:n).

It is important to ensure that the cardinality is correctly captured in the modelbecause it determines the detection of fact query subjects and it is used to avoiddouble-counting factual data.

When generating queries, IBM Cognos 8 follows these basic rules to apply cardinality:

Cardinality is applied in the context of a query.

1 to n cardinality implies fact data on the n side and implies dimension data onthe 1 side.

A query subject may behave as a fact query subject or as a dimensional querysubject, depending on the relationships that are required to answer a particularquery.

Possible end labels are

0..1 (zero or one match)

1..1 (exactly one match)

0..n (zero or more matches)

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Cardinalities in Cognos framework

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Kapil

I have been working for last 6years in Hyderabad India asBusiness Intelligence developer.I have worked on wide range ofreporting tools like

Cognos,Microstrategy, Logixml. Also i haveworked on Mutliple ETL toolsDatastage,Informatica, Pentaho. I am usingthis blog as a place to note down myexperience with issues. Usually i forget thingover time as most ppl do.So its good to keepa online journal.

View my complete profile

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Posted by Kapil at 18:35

Labels: cardinalities, cardinality, Cognos, Framew ork

1..n (one or more matches)

The first part of the notation specifies the type of join for this relationship:

an inner join (1)

An inner join shows all matching rows from both objects.

an outer join (0)

An outer join shows everything from both objects, including the items that donot match. An outer join can be qualified as full, left, or right. Left and rightouter joins take everything from the left or right side of the relationshiprespectively and only what matches from the other side.

Example

Cardinalities are set according to reporting needs and are not necessarilybased on data .Consider below example .Which will require a full outer join.

Consider example of sold date and product .there might be dates when noproduct were sold and there can be product which were never sold .so thecardinality shoud be 0:n :0:n (Full outer join)

but in actual case we want to see only products that were sold so we have1:1 to 1:n we can also model it to outer join 0:n to 1:n base on requirement

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