Virtual Gate Test Series: Databases - Referential Integrity

Question

We can convert any weak entity set to a strong entity set by simply adding appropriate attributes. Why, then, do we have weak entity sets at all?

 $1)$ We want to avoid the data duplication and consequent possible inconsistencies caused by duplicating the key of the strong entity

 $2)$ Weak entities reflect the logical structure of an entity being dependent on another entity

$3)$Weak entities can be deleted automatically when their strong entity is deleted

What is/are the possible correct reasons from the above:

$A)1$ and $2$                                            $B)2$ and $3$

$C)1$ and $3$                                            $D)1,2$ and $3$

Comments

D????

Answer 1

We can convert any weak entity set to a strong entity set by simply adding appropriate attributes.Why, then, do we have weak entity sets?

Answer :We have weak entities for several reasons:

•  We want to avoid the data duplication and consequent possible inconsistencies caused by duplicating the key of the strong entity.

•  Weak entities reflect the logical structure of an entity being dependent on another entity.

•  Weak entities can be deleted automatically when their strong entity is deleted.

• Weak entities can be stored physically with their strong entities.