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Transcript
Kennesaw State University Database Courseware Project (http://coffee.kennesaw.edu/) Mario A.M. Guimaraes ([email protected]) and Martha Myers ([email protected]) Database courseware (NSF) • design and develop animations in support of key database concepts. Current topics SQL (finished prototypes) Database Design (few prototypes) Concurrency (design, 1st prototype) SQL Queries – prototypes available • Visual Basic (downloadable) Visualization • Java (java applets) Construction & Visualization SQL Queries - motivation • Low student scores in tests involving queries • Construction: allows student to break SQL queries into parts and quickly access the results. • Visualization: Associating code that students already know with code they are unfamiliar. Database Design – prototype available (Flash) • Convert E-R Diagrams to tables 1) Scenario 2) E-R Diagram is drawn 3) User is presented with several options 4) For each selected option, feedback, animating data redundancy and null value is shown. E-R Diagram -> Table – motivation • Instructor may show several conversion options in a few minutes. • Students memorize or are given the solution (test results) • Students have trouble detecting redundancy Concurrency • Lost Update (being implemented) • Deadlock (being implemented) The Lost Update: A Concurrency Problem (table view) Trx1 requests and receives a Time 1 copy of X, 1000. Time 2 Trx2 requests and receives a copy of X, 1000. Trx1 decreases its value by 100 and returns the result Time 3 (900) to the database. Time 4 Trx2 increases the value 1000 by 200 and returns the new value (1200) to the database. Deadlock Trx1 requests and receives a copy of X, 1000. Trx2 requests and receives a copy of Y, 2000. Trx2 requests a copy of X, and enters wait Trx1 requests a copy of Y, and enters wait Next Prototypes • Database Design: Class Diagrams Object x Relational Normalization SQL Queries Indexes: B-Trees, Hashing, Bitmap