Expresses the minimum and the maximum number of instances of an entity B that can be associated with an instance of an entity A. The minimum and the maximum number of instances can be equal to 0,1, or N.
shows how many rows in one table related with other table these cardinality used by the desiner itself to detect valid query paths and to solve the loops
Cardinality expresses the minimum and maximum number of instances of an entity B that can be associated with an instance of an entity A. The minimum and the maximum number of instances can be equal to 0 1 or N.
The Main pupose for specifying a Cardinality is to resolve the Traps (Chasm / Fan). There is no way to identify the traps if the Cardinality is not known.
The idea behind cardinality is for checking the relationship among the tables whether it may be 1..1 1..m or vice versa and m..1. This relationship is checked based on key specification(primary or foreign key).
For example we cant able to create an account for a single customer in same name. So this mean 1..1 relationship between customer and account.
But No way it is connected for checking the trap or loop problem.
Expresses the minimum and the maximum number of instances of an entity B that can be associated with an instance of an entity A. The minimum and the maximum number of instances can be equal to 0 1 or N.
Cardinality means "How many instances of an Entity (on one side of the join) are related to the how many instance of another entity (on the other side of the join)"
Cardinality describes a join between 2 tables by stating how many rows of one table will match with rows of another table. It is very important to detect join problems and to create the contexts to correct the limitations of a target table.
BO designer can automatically detect and set cardinalities for each join. But we manually check the cardinalities based on the nature of keys that are joined.
Drag the column of first table to the corresponding column of second table or simply go to Insert->Join to create a join between 2 tables.
You can manually change the cardinality from n-n [many to many] or 1-n or n-1 or 1-1 and Click on "Detect". In BO It is always best to use 1-n cardinality for fast data retrieval. Always delete the unnecessary joins which have n-n cardinalty as these joins create loops.
