what is entry relationship data model ?give an ER diagram for a database showing fatherhood,motherhood and spouse relationship among men and womean.
Answers
Answer:
The entity-relationship model (or ER model) is a way of graphically representing the logical relationships of entities (or objects) in order to create a database. It is a designing tool used for designing a database. It is used to show the entities, relationship between entities, attributes of
entities along with the primary attribute of a database using graphical symbols.
Different symbols used in E-R diagram are:
1.
Rectangle, represents entity in ‘a database. An entity
can be a persoń, place or object whose data is stored in
the database.
2.
Oval, represents attribute of an entity. An attribute is
the properties or characteristics of the entity. If student
is an entity, its attributes can be st_id, st_name, st-
address, st_email etc.
3.
Oval with underlined text, represents primary attribute
(primary key). Primary key is used to uniquely identify
required data from the database.
4.
Diamond, represents relationship between two entities.
5.
Line, is used as connector between relationship and
entity, entity and attributes.
Explanation: