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

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1 Course Introduction Introduction 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

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7 Microarrays An Example of a New Sensing Technology A microarray The color of each spot represents the activity level of a gene under some experimental condition s of spots on a single chip

8 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...

9 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

10 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

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

12 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,...

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

14 Example: Internet Movie Database (IMDB)

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

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

17 A Schema Diagram for University DB (from the textbook) tables columns

18 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

19 MOVIE MID Title The Big Lebowski Star Wars Building a DB: Populate DB Rating R PG Director ACTS_IN PERSON MID PID Role Rtype PID Name Bday 1 1 The Dude STAR 1 Jeff Daniels 12/4/ Han Solo CO_STAR 2... Harrison Ford 7/13/42 Set initial records of the DB

20 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 FROM PERSON, ACTS_IN WHERE MID = 1 AND PERSON.PID == ACTS_IN.PID

21 Building the Application Program

22 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

23 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.

24 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

25 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

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

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

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

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

30 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

31 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