Page 13 - DCAP508_DATABASE_ADMINISTRATION

Unit 1: SQL Server RDBMS

1.4 Architecture and Database Objects Notes

Microsoft SQL Server is a Structured Query Language (SQL) based, client/server relational
database. Each of these terms describes a fundamental part of the architecture of SQL Server.

1.4.1 Database

A database is similar to a data file in that it is a storage place for data. Like a data file, a database
does not present information directly to a user; the user runs an application that accesses data
from the database and presents it to the user in an understandable format.
Database systems are more powerful than data files. The data is more highly organized. In a
well-designed database, there are no duplicate pieces of data that the user or application has to
update at the same time. Related pieces of data are grouped together in a single structure or
record, and relationships can be defined between these structures and records.
When working with data files, an application must be coded to work with the specific structure
of each data file. In contrast, a database contains a catalog that applications use to determine how
data is organized. Generic database applications can use the catalog to present users with data
from different databases dynamically, without being tied to a specific data format.

A database typically has two components: the files holding the physical database and the database
management system (DBMS) software that applications use to access data. The DBMS is responsible
for enforcing the database structure, including:
Maintaining the relationships between data in the database.
Ensuring that data is stored correctly, and that the rules defining data relationships are not
violated.

Recovering all data to a point of known consistency in case of system failures.
1.4.2 Relational Database

There are different ways to organize data in a database but relational databases are one of the
most effective. Relational database systems are an application of mathematical set theory to the
problem of effectively organizing data. In a relational database, data is collected into tables
(called relations in relational theory).
A table represents some class of objects that are important to an organization. For example, a
company may have a database with a table for employees, another table for customers, and another
for stores. Each table comprises columns and rows (attributes and tuples in relational theory). Each
column represents some attribute of the object represented by the table. For example, an Employee
table would typically have columns for first name, last name, employee ID, department, pay grade,
and job title. Each row represents an instance of the object represented by the table. For example, one
row in the Employee table represents the employee who has employee ID 12345.
When organizing data into tables, you can usually find many different ways to define tables.
Relational database theory defines a process, normalization, which ensures that the set of tables
you define will organize your data effectively.

Task Define the following:
1. DBMS
2. Relational Database

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