Database Management

Exploring the Territory

Database vs Flat Files

• Flat Files– Characters-fields-records-files

• Files are not designed to work together– Each file is an independent entity– No design rules followed– Updates can be hairy

• Databases– Files designed to work together

• Joins supported – fields from two or more files• Only redundancy is in linking (foreign) fields• Updates should result in few if any errors

Database Models

• Hierarchical– Resembles DOS tree structure

• Network– Hierarchical plus relationships that move two directions

• Relational– Offers set of underlying principles– Too much hype, too many fads, everything is relational,

lack of standards• Object Oriented

– Objects, classes, etc.

Our Goal

• Provide a correct up-to-date understanding of and appreciation for the most practical aspects of crucial database issues.

• Clarify concepts, principles, and techniques that trouble vendors and users

• Specific suggestions on how to deal with SQL implementations

Fads

• Vendors exploit ignorance– Obscure serious product deficiencies

• Panaceas for Database Management (that are/were not)– Internet Virtual Machines– PC SQL– ASP ColdFusion– Complex Data Types

Real Database Problem

• Failure of vendors and users to educate themselves

• Failure to rely on scientific foundation

• Use of ad hoc cookbook approach

• Self taught individuals who become DBAs

Fundamental Issues

• Database work needs to be approached scientifically

• No amount of expertise in a product or platform is sufficient in and of itself to address database design issues

• Consequences of wrong approach are severe• Designer needs knowledge and

understanding of fundamentals

Solution

• Database education – not product education• Identify the true database issues

– Unstructured data and complex date types

– Business rules and integrity enforcement

– Keys Quota queries

– Duplicates Redundancy

– Normalization & denormalization

– Entity subtypes and supertypes

– Data Hierarchies and recursive queries

Your Text

• Demonstrates how impractical and costly ignoring fundamentals can be

• Examples are from actual database projects and include specific SQL or other solutions

• Material is reasonably understandable to non-technical reader

• Compact – each chapter is 15 pages or less

Outcomes

• Understand central issues in database management• Avoid costly misconceptions and fallacies• Appreciate correct general solutions to core

problems• Assess if DBMS software offers a solution• Overcome, work around, or minimize

consequences when products do not offer solutions

Data Modeling Questions

• What information is in the system?• How is the information organized?• How can users obtain information they need• Questions to be answered

– What entities do we model

– What relationships exist between the entities

– What attributes describe the entities• What data types can be used to model the attributes

– Predefined – text, image, audio, video

Entity Relationship Diagram

• Technique for identifying entity types and diagramming relationships between entity types

• Determine predicates– Teacher has office– Professor teaches sections– Course has sections

Data Views

• Logical view– Soft view

• Screen output – query, report, etc.

– Hard view• Printer output

• Physical view– How data are stored on disk and what computer

has to do to find and retrieve data

Specialized Databases

• Multidimensional– Single file

• Geographical Information System GIS

• Types– Push or Pull– Preprogrammed or ad hoc

Data DictionariesMeta Data

• File Name• Field Name• Field Definition• Field Type• Column Heading• Field Length• Constraints• Validity Rules

Backup and Recovery

• Methods to Backup– Disk or tape; on-site or off-site; electronic

• Disaster Recovery– Cold sites and Hot sites– Disaster Recovery Plans

Search Engine

• An insult to relational database to use term to refer to search Engines

• A good topic for a future class – why search engines fails the relational database test

Information Characteristics

• Quality– Accuracy and precision; free of bias; complete,

timeliness, reliability of source

• Accessibility– Availability, admissibility

• Presentation– Level of summarization format

• Value and security