What is the importance of minimum cardinality in relation while-01372
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vu eng301 Business Communication.
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vu eng301 Mid Term Solved Past Paper No. 1.
Minimum Cardinality
This is a very important point, as minimum cardinality on one side needs special attention. Like in previous example an employee cannot exist if project is not assigned. So in that case the minimum cardinality has to be one. On the other hand if an instance of EMPLOYEE can exist with out being linked with an instance of the PROJECT then the minimum cardinality has to be zero. If the minimum cardinality is zero, then the FK is defined as normal and it can have the Null value, on the other hand if it is one then we have to declare the FK attribute(s) as Not Null. The Not Null constraint makes it a must to enter the value in the attribute(s) whereas the FK constraint will enforce the value to be a legal one. So you have to see the minimum cardinality while implementing a one to many relationship.
