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Database Management Systems: Understanding Databases and DBMS - Prof. Willis Boughton, Study notes of Computer Science

This chapter provides an overview of databases and database management systems (dbms). It explains what a database is, the advantages and disadvantages of using a database approach, fundamental database concepts, dbms roles, data definition, field types, queries and reports, data dictionary, data integrity, data security, and databases and the web.

Typology: Study notes

Pre 2010

Uploaded on 07/30/2009

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Chapter 14
Databases and Database
Management Systems
What Is a Database?
Database: a collection of related data stored in a
manner so it can be retrieved selectively
Database management system (DBMS): the
software used to create, modify, and access
databases
DBMSs available for PCs include:
Microsoft Access (most widely used)
Lotus Approach
Enterprise-level DBMSs include:
Oracle (the market leader)
IBM DB2
MySQL
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pf4
pf5
pf8
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Chapter 14

Databases and Database

Management Systems

What Is a Database?

Database: a collection of related data stored in a manner so it can be retrieved selectively

Database management system (DBMS): the software used to create, modify, and access databases

DBMSs available for PCs include: Microsoft Access (most widely used) Lotus Approach Enterprise-level DBMSs include: Oracle (the market leader) IBM DB MySQL

What Is the Database Approach?

Use databases, not just "regular" files for all data processing Using regular files is the file processing approach

Advantages:

Better information Faster response time Lower operating costs and storage requirements Improved data integrity and better data management

Disadvantages: Higher software cost Increased vulnerability (backup is essential)

Fundamental Database Concepts

A database consists of one or more tables

Each table contains information for one type of person, place, or thing, e.g., the Car table contains information for all cars

A table consists of one or more records Each record contains information for one person, place or thing, e.g., record 5 in the Car table contains the information for car

A record consists of one or more fields Each field contains one unit of information for that person, place, thing, e.g., the Color field contains the color for that car

Table demo

DBMS Roles

Users: use the DBMS to enter data, update data, write queries, and generate reports

Database designers: design databases

Define fields and rules for them

Database developers: create the databases

Use the DBMS and a programming language

Database programmers: write the programs to process information

Use the DBMS and a programming language

Database administrators: manage database security, access, and backup and restore

Data Definition

Data definition: the process of describing the characteristics of fields

Must be done for every field of every table

Each field must have:

Name (must be unique within the table) Data type (such as Text, Number, Currency, or Date) Properties, including: Field size (number of characters or bytes) Range of permitted values (number fields) Default value (initial value of the field) Format when printed, e.g., number of decimal places for a number

Field Types

Text: contains text, such as name and address

Alphabetic: contains only letters, e.g., "hello: Alphanumeric: contains letters and numbers, e.g., "abc123"

Number: contains a number such as a age

Date: contains a date Many possible date formats The unambiguous date format is dd-mon-yyyy

Currency: contains a currency number Has units such as dollars or Euros

Several other types common (^) Fields demo

Queries and Reports

A query selects records and fields from one or more tables and displays the selections

For example, select all records for "John Smith" You specify the criteria to be matched, e.g., the value of the name field must be "John Smith" Can have multiple criteria, e.g., "John Smith" and year "2000" You specify the fields to be displayed for each matching record

A report selects records and fields from one or more tables and prints the selections

Similar to query except printed in a format you select

Query demo

Data Integrity, Cont'd

Types of Data Validation

Alphabetic/numeric check: tests whether the correct type of characters are entered

Range check: tests whether the entered number is in the acceptable range Numeric fields only

Completeness check: tests whether the entry is complete, e.g., has entered a complete SSN

Consistency check: tests whether the entry is consistent with other data, e.g., if state is Illinois, country must be U.S.A.

Data Security

Data security: protecting data against destruction and misuse

Prevents access from unauthorized individuals

Required to maintain data privacy

Protects against data loss

Protects against intentional and accidental problems

Requires backup and recovery procedures

Disaster recovery plan: what to do if all databases are lost and must restore from scratch

Requires full offsite backup

Databases and the Web

Databases are commonly used on the Web for:

Information retrieval Dynamic Web pages (change based on user input) E-commerce