What do you understand by relationship type? How is it different from relationship instance and relatioship set?
What do you understand by relationship type? How is it different from relationship instance and relatioship set?
Whenever entities from different entity types are related to one another in a particular manner, they constitute a relationship type. The relationship prepared by between the two entity types vouchers and employees associates each voucher with the employee who prepared it. Similarly, the relationship authorised by between the two entity types' vouchers and employees associates each voucher with the employee who authorises it.
The degree of a relationship type is the number of participating entity types. A relationship type of degree two is called binary and that of degree three is called ternary. A VOUCHER (entity), Authorised by (relationship) and EMPLOYEES (entity) together signify a binary relationship. A SUPPLIER (entity) SUPPLY (relationship) PARTS (entity) to PROJECT (entity) signify a ternary relationship because three entities, namely supplier, parts and projects are participating in supply relationship in any transaction.
Relationship present at particular instance of time is known as relationship instance.
Relationship sets
1 : 1 (one to one relationship set)
1 : M (one to many relationship set)
M : M (many to many relationship set)
Whenever entities from different entity types are related to one another in a particular manner, they constitute a relationship type. The relationship prepared by between the two entity types vouchers and employees associates each voucher with the employee who prepared it. Similarly, the relationship authorised by between the two entity types' vouchers and employees associates each voucher with the employee who authorises it.
The degree of a relationship type is the number of participating entity types. A relationship type of degree two is called binary and that of degree three is called ternary. A VOUCHER (entity), Authorised by (relationship) and EMPLOYEES (entity) together signify a binary relationship. A SUPPLIER (entity) SUPPLY (relationship) PARTS (entity) to PROJECT (entity) signify a ternary relationship because three entities, namely supplier, parts and projects are participating in supply relationship in any transaction.
Relationship present at particular instance of time is known as relationship instance.
Relationship sets
1 : 1 (one to one relationship set)
1 : M (one to many relationship set)
M : M (many to many relationship set)
