C. Relational Database
Relational database, as a database, which is based on
the relational database model, uses the concepts and
methods such as algebra of sets and so on to process the
data in the database.
The architecture of the relational database can be
divided into four levels: Database, Table and View,
Record and Field. And the terms of the corresponding
relational theory is database, relation, tuple and attribute,
which are described as follow.
Firstly, Database: Relational database can divide into
local database and long-distance database according to the
way of data storage and the way of accessing by users.
Comparing with the local database and long-distance
database, the former can access faster, but the latter has
bigger volume of storage and it can adapt to several users
to access. To use which one, it depends on many factors
such as how many data should be stored and processed,
how many users access the database in the same time, the
demand of performance of database and so on.
Secondly, Table: The primary elements of relational
database are some tables of storage data. The table in
database is very simple in logical structure. It is composed
of several rows and columns. It can’t contains a table
inside a table. It requires every unit in table only has one
data which can be alphabetic string, number, monetary
value, logical value, time and some simple data.