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+2 votes
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1:1

 

1:M

 

M:1

 

M:N

in Databases by Loyal (6.3k points) | 781 views

1 Answer

+3 votes
Best answer
A weak entity it self doesn't have a primary key and depends on the strong entity to form a primary key. For example EMPLOYEE can be a strong entity and DEPENDENT a weak entity. An employee can have multiple dependents and a dependent can have multiple concerned employees. So, the relationship is M:N, with the participation of weak entity being TOTAL- there is no dependent without a concerned employee.
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Sir, but there can be total participation of weak entities when the relationships are other than M:N also..i think sir it depends on the requirement analysis....please correct me if wrong..
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Sir and EMPLOYEE and DEPENDENT is generally 1:M
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Total participation is irrespective of whether it is 1:N or M:N. Because there can be no dependent without the corresponding Employee.

To be clear, DEPENDENT is Dependent of

So, one employee can be dependent of many other employees. Also, same employee can depend on multiple other employees. Hence, M:N. But, this is just an example- the main thing is the relationship between weak entity and strong entity can be M:N.
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relationship can be 1:M,1:1 and M:1 also..righ sir? because total participation is independent of the relationship...is this correct

?
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yes. but we should say M:N because of all possibilities.
+1
ok got it sir...thank you..
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So, one employee can be dependent of many other employees

Also, same employee can depend on multiple other employees. Hence, M:N. 

here both entities are employees so they both are strong  none of them is weak.

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Arjun sir, if it is m:n, in that case we won't be able to uniquely identify weak entities...it has to be 1:m...pls correct me..
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Sir, If M:N relationship is possible, how to generate table for the weak entity set? Do we have to introduce a third table? If so,  will weak entity set continue to have partial keys alone? Please clear my confusion sir...
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