Databases

Tom Kelliher, CS14F

Oct. 29, 1996

What is a database? Organized collection of information.

What are operations associated with a database?

1. Store information.

2. Organize information.

3. Retrieve information.

Two types of databases:

1. File management system --- single file.

2. Database management system --- multiple files, relationships between files.

How would an individual use a database?

How would an organization use a database?

Is the World Wide Web a database?

What are the impacts upon society?

Parts of a Database

1. File --- Usually a binary file in a proprietary format. Contains records.

2. Record --- Information about one ``entity.'' Contains fields.

3. Field --- One ``bit'' of information about an entity.

Abstract view of a database:

Note: each record has same number of fields.

Database Example

Catalog of CDs:

1. One record for each CD.

2. Fields:
   1. Title.

   2. Artist.

   3. Year.

   4. Type (alternative, classical, jazz, etc.)

   5. Label.

   6. Track number.

   7. Track title.

   8. Order number.

Can we put all the track titles into one record?

File Management Systems

1. Flat file systems.

2. Single file databases.

3. No linking to other files.

4. Only one ``view.''

5. Redundancy (consider CD example).

Database Management System

1. Relational database.

2. Multiple files.

3. Relationships between files.

4. Relational model:
   1. Entity.

   2. Relationship.

5. Key field (sometimes multiple fields).

6. Redundancy elimination. Why is redundancy bad?

Example

DBMS Software Components

1. Data Definition Language.

2. Data Manipulation Language.

3. Query Language (SQL).

4. Report Generator.