what is cardinality

[Former Member]

dear masters,

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Edited by: Alvaro Tejada Galindo on Feb 6, 2008 12:23 PM

[Former Member]

http://en.wikipedia.org/wiki/Cardinality

[former_member156446]

Definition of: cardinality

A quantity relationship between elements. For example, one-to-one, one-to-many and many-to-one express cardinality.

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cardinality refers to the number of members in the set. When specifically applied to database theory, the cardinality of a table refers to the number of rows (or tuples) contained in a table.

[Former Member]

hi,

I Think this will Help U to Understand Cardinality .

Cardinality (n:m) describes the foriegn key relation ship with regard to number of possible dependent records ( Records of Foreifn Key Table) or Referenced Record .

n = 1.

There is exactly One Record Asssigned to Check Table For Each record of forign Key Table.

N = c.

the forign Key Table may contain Record Which Donot Correspond To check Table Because The Foriegn Key field IS empty.generally this case occurs where forign key is optional.

m= 1. 1 record for each record in check table.

m = c ..there is at most one record for each record in check table.

m =n . there is at least dependent record for each record of check table.

<REMOVED BY MODERATOR>

Edited by: Alvaro Tejada Galindo on Feb 6, 2008 12:34 PM

[Former Member]

Hi,

Not sure in what context your using cardinality. But I use this term for database tables usually.

For example:

1-1: This means that the relationship between 2 tables is one on one. This means that a record in table A will only have one matched record in table B.

1-N: This means that the relationship between 2 tables is one to many. This means that one record in table A will have N matched records in table B.

N-N: This means that the relationship between 2 tables is many to many. This means that N records in table A will have N matched records in table B.

Hope it helps.

Regards,

Gilberto Li

[Former Member]

Cardinallity defines in what way the indexes are goign to be made on the dimenasion for which you define it.

With Line Item Dimension, you can assign ONE Dimension to only one characteristic.

With Cardinality, you can assign a Dimension containing Multiple Characteristics.

The scenario totally depends on what is the size of the Dimension Table w.r.t Fact Table. If it is greater than 10% of Fact Table then you need to consider about these.

Cardinality creates indexes on the Dimension table entries and there by you would see an improvement in performance.

Check this thread for Line Item and High Cardinality Use

http://help.sap.com/saphelp_nw04/helpdata/en/a7/d50f395fc8cb7fe10000000a11402f/frameset.htm

A node is a container for node elements. The cardinality determines how many elements may be contained at runtime in a node.

0:1 = at most one

1:1 = exactly one

0:N = any number

1:N = at least one

For 1:1 and 1:N, the framework guarantees that there is always at least one element in a node. You can rely on this and don't need to create an element in your application.