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Course Introduction Introduction to Databases

Course Introduction Introduction to Databases. Instructor: Joe Bockhorst University of Wisconsin - Milwaukee. First Reading Assignment. Chapters 1 and 2 (today and part of Thursday) Chapter 13 and handout.

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Course Introduction Introduction to Databases

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  1. Course IntroductionIntroduction to Databases Instructor: Joe Bockhorst University of Wisconsin - Milwaukee

  2. First Reading Assignment • Chapters 1 and 2 (today and part of Thursday) Chapter 13 and handout

  3. “There's a prayer each night that I always pray:Let the data guide me through every day”Warren Zevon

  4. Data is Ubiquitous • Three classes of technological advances are changing our relationship with data: • More storage space • allows us to keep more data • Faster processor (and memory) speeds • allows us to access and process more data • Different “sensors” • allows us to access new kinds of data

  5. http://en.wikipedia.org/wiki/Hard_disk

  6. Microarrays – An Example of aNew Sensing Technology The color of each spot represents the activity level of a gene under some experimental condition 10 000s of spots on a single chip A microarray

  7. Other Data Examples • Airline flight management system • Financial data • Commercial store (eg, WalMart) data • Department of Motor Vehicles • Surveillance video • University student records • Baseball results • Web sites • Medical records • ...

  8. Effectively Data Management is Essential • Organizations need their data to be an asset • Given: the amount of data available to store & costs to manage data (hardware, software, labor) • Ineffective policies can make an organization’s data a liability

  9. Database Management System (DBMS) • DBMS is: • A collection of software programs • General purpose • DBMS enables users to: • Define DB • Construct DB • Change (or update) DB • Ask questions about the data in DB • Share DB • DBMS maintains the integrity of DB

  10. Some RDBM Systems Commercial Systems Oracle ($$$$) DB2 (IBM) ($$$) SQL Server (Microsoft) ($$) Open Source Systems PostgreSQL MySQL Source: International Data Corporation

  11. Main Goals of this Course • To understand how to use a DBMS • How to create DB, data models, SQL,... • To understand how a DBMS works • Physical properties of disks and files, software to manage reading and writing to disk, implementation of algorithms to answer user queries,...

  12. catalog Databases are self-describing: catalog describes the structure of the data stored in the DB

  13. Example: Internet Movie Database (IMDB)

  14. Building a DB: construct a conceptual model • A conceptual model identifies entities and relationships role type role acts in release date title name birthdate N M movie person N 1 director of relationship entity attribute

  15. A schema describes DB using data model supported by DMBS (eg, relational model) RDBMS – DBMS that supports relational model MID Title Rating Director PID Name Bday MID PID Role Rtype Building a DB:Define DB Schema MOVIE PERSON ACTS_IN

  16. A Schema Diagram for “University” DB(from the textbook) tables columns

  17. Building a DB:Describe Physical Data Model • PDM indicates how data is organized on disk • Includes description of access paths or indexes • Example: store “Movie” table with records ordered by MID and construct an index on the “Title” attribute 1 The Big Lebowski R 99 2 Star Wars PG 16 The Big Chill The Big Lebowski 270 The Big Chill PG 3 Index on Title column File of records of the MOVIE table

  18. Building a DB:Populate DB MOVIE ACTS_IN PERSON Set initial records of the DB

  19. Querying The Database • Most RDBMS allow users to query the database using SQL (structured query language) • Example: get cast of “The Big Lebowski” SELECT Name, Role, Rtype FROMPERSON, ACTS_IN WHERE MID = ‘1’ AND PERSON.PID == ACTS_IN.PID

  20. Building the Application Program

  21. Implementing Queries • “Relational Algebra” is a mathematical way to describe operations on relational data • SQL queries correspond to sequence of relational algebra operations • The previous query requires a join operation between person and acts_in • Query Optimization involves finding a good order to carry out operations • Operator implementation

  22. Managing Physical Data Storage • RDBMS maintains database (and meta-data) on non-volatile storage (hard disks) • Physical design impacts RDBMS performance • Example: The time to answer a query such as What is the MID of “The Big Lebowski” can be greatly reduced if an index of Title column is maintained for the Movie table.

  23. Maintaining Integrity of the Database • Concurrent users • Multiple users may attempt to update simultaneously • Security • Preventing unauthorized access • System failures • If lightening strikes during an update the DB must able to be recovered

  24. Summary of Topics • Conceptual modeling • Logical Modeling • Querying the DB • Building applications • Implementing Queries • Managing hardware • Maintaining Integrity how to use DBMS how a DBMS works

  25. Control Abstraction User Application Program Each layer need not know (or care) how other layers are implemented Query Optimization Relational Operators DBMS Files and Access Methods Buffer Management Disk Space Management DB

  26. Data Abstraction Each layer need not know how other layers organize data

  27. Why Use DBMS? • Program Data Independence • Controlling redundancy • Providing backup and recovery • Efficient query processing • Others: see Section 1.6

  28. Why not to use a DBMS? • Consider custom software if DBMS overhead (cost, complexity, performance) is unnecessary • Example: single user of fixed dataset

  29. Schemas and Instances • A schema describes a database • RDBMS typically store schemas in the catalog • The actual data in the DB at a particular time is the database state • The current set of all instances in the DB

  30. People who work with DBMSs • Database Administrator DBA • Maintains databases, DBMS and related software • [avg salary* $76k] • Application Programmers • Software engineers (developers) that build software solutions for end users that access DBMS • End Users • Example: bank teller uses “canned transactions” • DBMS designers and implementers • Example: Oracle developers *source: payscale.com, 2007

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