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Good Afternoon!
I’m trying to understand about Cardinalidade Minima and Cardinalidade Máxima between different entities!
What I know so far is :
A Cardinalidade Minimacan be aAtributo Opcional(0)or aAtributo Obrigatório(1)
A Cardinalidade Máximacan be aAtributo Monovalorado(1)orAtributo Multivalorado(N)
My question is, how will I determine the cardinality of the attributes?
It will be from the relations between the two attributes (for example A and B) for both cardinalities?
Or at least cardinality I have to see whether the attribute is mandatory or not, and at most I have to see how many attributes of A relate to how many attributes of B and how many attributes of B relate to the attributes of A?
One-to-one, one-to-many, many-to-many. A person can have 0-n children. One person can be married to 0-1 persons, 1-n suppliers can provide p/1-m companies
– jean
Jean, my doubt is not this unfortunate! About the type of cardinalities I understood, my doubt is how I do to through an exercise or data provided manage to identify whether: it is mandatory or optional at least and whether it is multi or mono at maximum!
– Carol M
unhappyzmind that depends on case-by-case and can be dictated by the requirements of the system. Example: In a table of parents of students each parent will have at least one child while in a table of people each one can have children or not
– jean
then I will only know how to classify according to the case you have in hand?
– Carol M
In relation to the data set the answer, 99.9% of the time, begins with: depends...
– jean
thank you jean!!
– Carol M