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INTRO TO DATABASES PART II IS 340 BY CHANDRA S. AMARAVADI 1 IN THIS PRESENTATION.. DBMS evolution file processing, hierarchical, relational ER Models Distributed databases Multi-media databases Data warehouses 2 DBMS EVOLUTION 3 EVOLUTION OF DBMS File processing systems Hierarchical systems Person 1 March 2002 Greece 2 July 2003 Italy 3 …………….. Photo1 Greece Photo2 Italy Relational systems PhotoId 4 EVOLUTION OF DBMS.. FILE PROCESSING SYSTEMS: A system where data was managed by the program in the form of flat files. Data in the form of “flat files” (ascii files) Each program had its own specific files Data was duplicated across files. 5 EVOLUTION OF DBMS.. PROBLEMS CAUSED BY FILE PROCESSING Uncontrolled redundancy Poor data quality (a.k.a.?) Lack of data sharing 6 HIERARCHICAL MODEL A model for storing data: structure is hierarchical (not flat) one or more root segments child segments are linked hierarchically difficult to write queries but very efficient (fast)! 7 HIERARCHICAL MODEL (D) DEPARTMENT NAME (A) ADMIN-STAFF ASNAME JOB_TITLE TOTAL_ENROLL NO_OF_PHD (F) FACULTY FNAME RANK DEGREE What do you call this? 8 RELATIONAL MODEL Data organized into tables Data retrieved by using SQL, 4th GL joins tables by equating values of cross reference keys. ACCT ACCT# NAME DT. OPENED 8895 8896 8897 Smith Farley Gomez 4/16/00 4/22/01 1/10/00 BALANCE $35,000 $300 $2,000 9 ER MODELS (Data Models) 10 DEFINITIONS Entity – Individual example of person, place or thing. Entity Class – Collection of related entities. Attributes – Properties of entity classes about which we would like to collect information. 11 AN EXAMPLE ER CHART Cust# Name ENTITY CLASS CUSTOMER ATTRIBUTE RELATIONSHIP places ORDERS Ord# are for PRODUCTS Ord dt 12 DISCUSSION Draw Data Models (ER models) corresponding to the following Situations: Athletes participate in events (qualifier, semi-finals, finals) in various sports (swimming, boxing etc.). Clients can book one or more properties with a rental agency. Each property can be booked by more than one client (for different dates). Trains arrive and depart from platforms in train stations, corresponding to the cities that they stop in. A city can have many Stations. Airlines operate a number of flights which arrive and depart from Gates. There could be several flights from a gate, but each flight is assigned only one gate. Each airline operates a gate or a set of Gates which are leased to them by the airport. 13 DISCUSSION Design a database for the following situation: Bellsouth, a telephone company needs a database to maintain records of its automobiles, repairs, mechanics and special equipment needed to repair cars. Mechanics are assigned skill codes based on the type of repairs they can carry out. For e.g. Class III mechanics can perform reborings, engine overhauls and transmission repairs. The repair shops are located in 300 cities and towns throughout the state. Mechanics can be assigned to only one repair shop at a time. The application requires knowing what equipment is (for e.g. diagnostic equipment, hydraulic machinery) is at what location and also the repairs carried out on each vehicle. For each vehicle the application requires knowing its identification number, mileage and repair history. 14 DISTRIBUTED AND MULTI-MEDIA DATABASES, DATA WAREHOUSES 15 CENTRALIZED DATABASES Centralized databases The database is in one physical location. All applications regardless of whether the clients are located in Seoul or Detroit need to access data from that physical location. What are the limitations? 16 DISTRIBUTED DATABASES The data is physically stored in multiple geographical locations Replicated -- copies of the database maintained in multiple sites Partitioned -- database is physically divided into chunks 17 REPLICATED DATABASES.. 18 PARTITIONED DATABASES.. Emp ID Emp Name Emp Address 11049 Richard 200 Meadow brook 11051 Cathy 13 E. Willow 11054 Hugh 1400 E. Washington 19 MULTI-MEDIA DATABASES A database that is able to handle multiple data types: Conventional information Images Audio & video Capable of storing, retrieving and updating this type of information Emp ID Emp Name Emp. Picture Emp Address Emp.jpg 20 MULTI-MEDIA DATABASES.. APPLICATIONS Travel bureaus Hospitals Manufacturing Training 21 MULTI-MEDIA DATABASES.. ISSUES Storage space Retrieval Modification 22 DATA WAREHOUSES DATA WAREHOUSE: Historical data organized for analysis and decision making. DATA MART: smaller version of data warehouse, specialized by functional area e.g. marketing ON-LINE ANALYTICAL PROCESSING (OLAP): organizes data into a “cube” for decision analysis. 23 DATA WAREHOUSING & OLAP OPERATIONAL, HISTORICAL DATA INTERNAL DATA SOURCES DATA WAREHOUSE EXTRACT, TRANSFORM HISTORICAL INFORMATION OLAP DATA MINING EXTERNAL DATA SOURCES 24 DISCUSSION QUESTIONS Are Databases and DBMSs one and the same? Does a record consist of files? What is the smallest unit of data in the database? Does data integrity refer to data quality? What does the detail line of a report consist of? Is an “employee” an entity class or an attribute? Is the data dictionary useful while creating the database? Why do we use SQL? Is it necessary to use SQL to produce database reports? Why do we use data models? Would multi-national organizations prefer centralized databases? 25 THAT’S ALL FOLKS! 26