What is Entity in Database?
A person, place, object or event in the user environment about which the organization wishes to stores information about. Some specific examples of entities are Employee, Student, Lecturer. An entity is analogous to a table in the relational model. E.g. Teacher is the entity, about which is to make a records.What is Attributes in Database?
A property or characteristic of an entity or relationship type that of the interest of the organization is called Entity. E.g Teacher is entity and their name,, age, contact number etc is the attributes. The above diagram clearly shows it
Relationship and Relation
A relationship is an association (link) of entities where the association includes one entity from each participating entity type.
While a relation is a named two dimensional tables of data. Each relation consists of a set of named columns and a number of rows.
Relational Database
A database that represents data as a collection of tables in which the relationship are represented by common fields in the related tables.
Entity type
A collection of entities that shares common properties
Types of Entities
- Strong entity type
An entity type that exists independently of other entity types
The strong entity type is called the identifying owner
- Weak entity type
An entity type whose existence depends on another entity type.
Cardinality Constraints
The number of instances of one entity that can or must be associated with each instance of another entity.
Written by Faraz
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