Description about weak entity sets in DBMS

Weak entity sets, Description about weak entity set, Information about weak entity sets, Example weak entity set

Weak Entity Sets

Information about Weak Entity Sets

Properties	Description
Definition	An entity set that may not have sufficient attributes to form a primary key is called as weak entity set.
Association	Every weak entity set must be associated with an identifying strong entity set.
Existence dependent	Weak entity set is said to be existence dependent on the identifying strong entity set.
Owner / Identifying entity set	The entity set on which the weak entity is dependent is the owner or identifying entity set.
Identifying Relationship	The relationship set between the owner and weak entity sets is called identifying relationship.
Type of identifying relationship (Cardinality ratio)	Many-to-One from weak entity set to the owner entity set.
Key of Weak Entity set	The key is called as Discriminator or Partial key.
Participation of weak entity set in the relationship	It is total participation.
ER Diagram Notations	Double rectangle – Weak Entity set Double diamond – Weak relationship set Double line – Total participation Dashed underlined attribute - Discriminator

A weak entity set can participate in other relationships as well.

A weak entity set can have more than one identifying entity sets.

Example:

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 Weak entity set - An example

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