CODEWITHSUNDEEP
databasedatabase-designdata-modelingentity-relationship
eeoab48
eeoab48

Reputation: 11

Modelling ER diagrams with weak entities

If an entity, say x, is dependent on multiple other entities but x does not have any key attributes (so x can not be a weak entity?). Then how should x be modelled in an ER diagram, assuming x has attributes and x has relationships with other entities (that it is not dependant on).

Upvotes: 1

Views: 646

Answers (1)

Amira Bedhiafi
Amira Bedhiafi

Reputation: 1

By definition, entity sets which do not have sufficient attributes to form a primary key are known as weak entity sets and the entity sets which have a primary key are known as strong entity sets.

Weak entities are represented with double rectangular box in the ER Diagram and the identifying relationships are represented with double diamond. Partial Key attributes are represented with dotted lines.

A very common example, Payment and Loan Payment. Payment is the weak entity. Loan Payment is the identifying relationship and Payment Number is the partial key. Primary Key of the Loan along with the partial key would be used to identify the records.

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Upvotes: 1

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