Transcript Mar10IntroDB

INFS215
Introduction to Databases
Subash C. Biswas
Questions
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What is a database?
Why a database is so important?
What are the basic components and types of
databases?
What is an entity, attribute, identifier,
relationships, cardinality (min & max)?
What is referential integrity?
What is an ERD?
Basic Concepts
People
Data
(raw)
Hardware
Software
Procedure
Data
Data
(Information)
Components of A Database
System
Application Programs
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Functions:
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Create and process forms
Create and transmit queries
Create and process reports
Execute application logic
Control application
DBMS
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DBMS: Database Management System
Functions:
 Create database, tables, and supporting structures
 Read and update database data
 Maintain database structures
 Enforce rules
 Control concurrency
 Provide security
 Perform backup and recovery
Example: Oracle, DB2, Microsoft Access,
SQL Server
Database
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Database is a self-describing collection of related records
or tables
Components:
 User Data
 Metadata: data about the structure of a database
 Indexes and related structures
 Stored procedures: program modules stored within the
database
 Triggers: a procedure that is executed when a particular
data activity occurs
 Application metadata: data describing application
elements such as forms and reports
Types of Database
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Personal database
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Workgroup database
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1 user; < 10 MB
< 25 users; < 100 MB
Organizational database
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Hundreds to thousands users
>1 Trillion bytes, possibly several databases
Example:
Organizational Database
Binary Relationships
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1:1
1:N
N:M
Domains
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A domain is a named set of values that an attribute can
have
It can be a specific list of values or a pre-defined data
characteristic, e.g. character string of length less than 75
Domains reduce ambiguity in data modeling and are
practically useful
Data Types
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Standard data types
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Char for fixed-length character
VarChar for variable-length character
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It requires additional processing than Char data
types
Integer for whole number
Numeric
Normalization
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Normalization eliminates modification anomalies
 Deletion anomaly: deletion of a row loses information
about two or more entities
 Insertion anomaly: insertion of a fact in one entity cannot
be done until a fact about another entity is added
Anomalies can be removed by splitting the relation into
two or more relations; each with a different, single theme
However, breaking up a relation may create referential
integrity constraints
Intersection Tables