B.Tech experiments lab

EXPERIMENT - 2

ER DIAGRAM FOR SAILOR BOAT DATABASE

Aim:

Draw an ER diagram of sailors database.

Components of ER diagram

Entity – An entity is an object that exists in database administration.

Attribute – In DBMS an attribute refers to a database component, such as table.

Primary key – A primary key is a specific choice of a minimal set of attributes that uniquely specify a tuple in a relation.

Foreign key – A foreign key is a set of attributes in a table that refers to the primary key of another table.

Composite attribute – It is an attribute where the values of that attribute can be further subdivided into meaningful subparts.

Derived attribute – These are the attributes that do not exist in physical database, but their values are derived from other attributes present in the database.

Relationship – A relation as originally defined by E.F. codd. Is a situation that exists between two relational database tables.

Ternary – A ternary relationship is an association among three entities.

Many to many – refers to a relationship between tables in a database when a parent row in one table contains several child rows in second table, and vice versa….

ER DIAGRAM