E-R and EER Models: Types of Entity Sets

There are two types of entity  sets as given below:

1. Strong Entity Sets

Entity set having any  key attributes are known as Strong Entity  sets.

Ex. The Figure  2.12 shows strong  entity set Student  having key attribute  Reg_No.

2. Weak Entity Sets

Entity sets having no key attributes are known as Weak Entity sets.

Ex. The Figure 2.13 shows weak entity set Table having no key attributes to identify the tuples uniquely.

A weak entity set is always associated with another entity set to make it meaningful. This another entity set is known as Identifying entity set.

Source: Gupta Satinder Bal, Mittal Aditya (2017), Introduction to Database Management System, 2nd Edition-University Science Press (2017)

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