Ø Database schema –
· Design of a database is called the schema.
· A database schema is the skeleton structure that represents the logical view of the entire database.
· It defines how the data is organized and how the relations among them are associated.
· It formulates all the constraints that are to be applied on the data.
· A database schema defines its entities and the relationship among them.
· It contains a descriptive detail of the database, which can be depicted by means of schema diagrams.
· It’s the database designers who design the schema to help programmers understand the database and make it useful.
A database schema can be divided
into three categories –
1) Physical
schema
2) Logical
schema
3) View
schema
·
Physical Database Schema −
this schema define the actual storage of data and its form of storage like
files, indices, etc. It defines how the data will be stored in a secondary
storage.
·
Logical Database Schema −
this schema defines all the logical constraints that need to be applied on the
data stored. It defines tables, views, and integrity constraints.
·
View schema – view schema
can be defined as the design at database at view level which generally describes
end users interaction with database.