Welcome To Series Articles of DBMS (volume-2)
Data model: It is known as the design of database management system, which can be used for the creation of a different kind of data model.
Types:
1)E-R model (entity-relationship model).
2)Relational model (Table).
3)Hirercial model.
2)Relational model (Table).
3)Hirercial model.
1)E-R model: the basic requirement of the E-R model are the entity, attribute, and relationship.
E-R model consists of an entity and an attribute.
E-R model consists of an entity and an attribute.
1.Entity: the real-world object which is having the physical existence. the pictorial representation of an entity is the rectangle.
Ex:
2.Attribute: the description of the particular entity, which is known as a collection of different objects is identified as an attribute. The pictorial representation of attribute is oval.
Ex:
Types of attributes: Simple attribute, Composite attribute, Multi-value attribute, Derived attribute.
1.Simple attribute: it consists of a single value and it must be atomic.it cannot be further divided.
Ex:
2.Composite attribute: when an attribute is derived it is known as a composite attribute. It can be further divided.
Ex:
3. Multi-value attribute: when an attribute has more than one value is known as a multi-value attribute. the pictorial representation of multi-value attribute is double oval.
Ex: A single person can have more than one phone number.
4. Derived attribute: if the attribute is derived from another attribute is known as a derived attribute. the pictorial representation of derived attribute is dotted oval.
Ex:
I hope this article is useful to you, plz follow the next volume for more information, please post your doubts in the comment box.
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