Transcript Database Management

Databases and Database
Management Systems
What is a database?
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A database is a file of similarly structured
records.
A database is a collection of information
related to a particular subject or purpose,
such as tracking customer orders or
maintaining a music collection.
What is a database
management system (DBMS)?
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A database management system is software
that allows you to manage all your data in a
systematic fashion.
It allows you to design and create new
databases and perform various operations on
existing databases.
These operations include adding new data and
retrieving, modifying or deleting existing data.
Types of DBMS architectures
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Network (e.g. Cullinet Software’s IDMS)
Hierarchical (e.g. IBM’s IMS)
Relational (the most common in use
today)
Object-relational
Object
Example relational DBMSs
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“Large”
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Oracle
DB2 (IBM)
Informix
Sybase
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“Small”
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Access (Microsoft)
FoxPro
dBase
4th Dimension
Most common DBMS model on
market?
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Relational
The relational DBMS we will
be using in the course?
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Access, which is part of Microsoft Office
Two components of employing
a DBMS
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Designing and building the database
Manipulating the data
Steps in building a database
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Choose a DBMS
Define the data structure (Data
Definition)
Create or import a set of records
Steps in using a database
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Data Manipulation:
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Insert
Retrieve
Update
Delete
Sort
Calculate, etc.
Recovery, Security, etc.
Building a database
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In the relational data model a database
consists of one or more tables. (Each
table is called a relation, hence the
name relational.)
Each row in one of these tables is a
record.
A record consists of a set of fields.
What is a database schema?
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A database schema consists of all the
information about what the tables are,
what the fields are within each record in
each table, how the tables are related,
etc.
If you take an existing database and
delete all the records, what’s left is the
underlying database schema.
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So the first step in building a new
database is to create the underlying
database schema.
A major component of this is to tell the
DBMS what the structure of your
records will be (Data Definition) within
each table.
There are three main steps in
data definition
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Naming each field in a prototypical
record,
Specifying its datatype, and
Specifying its size, if appropriate.
Data validation
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One of the main features of a DBMS is
to perform data validation when a user
attempts to create a new record or
modify an existing record.
The reason for specifying a datatype for
a field is to allow the DBMS to check
the validity of user-entered data and
reject invalid data.