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) –InternetVirtual Machines –PCSQL –ASPColdFusion –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 –KeysQuota queries –DuplicatesRedundancy –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 Dictionaries Meta 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