Friday, January 1, 2010

Differences among an entity, an entity type, and an entity set.

A set of entities that have the same attributes is called an entity type. Each entity type in the database is described by a name and a list of attributes. For example an entity employee is an entity type that has Name, Age and Salary attributes.
The individual entities of a particular entity type are grouped into a collection or entity set, which is also called the extension of the entity type.
An entity is a thing in the real world. It may be an object with a physical existence or an object with a conceptual existence. A set of these entities having same attributes is entity type and collection of individual entity type is an entity set.

6 comments:

Jules Bartow said...

How about an example?

I'm a database weenie - are these roughly the correct parallelisms?

Entity ~ Table
Entity Set ~ Rows in a Table
Property ~ Columns in a Table

What do you mean by an entity type

Jules Bartow said...

How about some examples?
I'm a database weenie - are these roughly the correct parallelisms?

Entity ~ Table
Entity Set ~ Rows in a Table
Property ~ Columns in a Table

Anonymous said...

No jules,

Entity type is a table.
And the entity set will be collection of few records(tuples).

For eg. Me and You are individual entities, whose entity type is "HUMAN BEING" and we have a similar set of attributes(columns of the table "HUMAN BEING"), and me,you and some of our friends,who share common attributes become the entity set.

Iamateur said...

I feel if name is the attribute and name is the entity type then its entity set will be first name,middle name,last name. what say am I right?
Clarify me.

mujahid islam said...

I have search a lot, but still i am confuse that what is the difference between Entity and Entity Type.
can any one briefly explain it?

Unknown said...

If u r familiar with Java.. U can think of it like entity as an object. Entity type as class.. And entity set group of objects