An Introduction to Database Management Systems R. Nakatsu

Why do we need a database? n Data is easier to manage  Too much data in individual files  Too many separate files n Need multiple views of data n Improved data sharing (concurrent updating) n Improved data security n Databases can better enforce data quality n Leads to better data integration

File-Processing Systems

Problems with File-Processing Systems n Data are separated and isolated n Data are often duplicated n Incompatible data files n Program-Data Dependence

Databases are Centralized

What is a database? n A database is an integrated collection of logically related data elements. A database consolidates records previously stored in separate files. n A database can be viewed as the topmost element of a data hierarchy:  database (a set of related files)  file (a collection of related records)  record (a group of logically related fields)  field (an attribute)  character (single alphabet, number, or other symbol)

Database Systems, 9th Edition

TableRowColumn FileRecordField RelationTuple**Attribute Related Terminology: Three ways to refer to the same thing **Rarely used terminology

Database Components Page 26 © 2000 Prentice Hall

Types of Data 1.User data 2.Metadata 3.Indexes 4.Application Metadata

1. User Data n A table of data is called a relation n Columns are fields or attributes n Rows are specific instances n Relations must be structured properly

2. Metadata or Data Dictionary “a description of the structure of the database” System tables store metadata, including:  table names  field names  primary key fields  data types  field size  data constraints (e.g., input masks, and validation rules)  relationships between tables

3. Indexes n Improve performance n Improve accessibility n (Overhead data)

Physical vs. Logical Storage n Physical Storage is how the computer actually stores the data n Logical Storage is how the human end-user views or perceives the data Indexes create a logical view on your data.

4. Application Metadata Stores the structure and format of:  forms  reports  queries  other application components

Hierarchy of Data Elements

Database Management System (DBMS) A DBMS (database management system) is a set of computer programs that is used to create, maintain, and provide controlled access to user databases

DBMS: Main Functions n Data definition  Define what data is stored, the type of data, how the data is related.  You can also specify how the data can be formatted and validated n Data manipulation  You can select which data you want, filter it, sort it, join it with other data, summarize it. n Application Development  Graphical tools to develop menus, forms, and reports n Data control  Allows you to specify security, transaction management, backup and recovery

Databases for Competitive Advantage: Walmart Continuous Replenishment System:  Point of sale terminals record the bar code whenever a customer purchases a product.  A database stores inventory data  Suppliers can access Walmart’s sales and inventory data online using the Web.

Strategic Information Systems Computer systems that help the organization gain a competitive advantage. Systems can be created to: Explore, identify, and occupy new market niches. Understand the customer value chain better. Learn faster and more deeply than competitors.

RECAP n Why do we need a database? n File processing systems vs. databases n What is a database? n The DBMS n The four types of data n Databases for Competitive Advantage