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behind the scenes- databases and info systems.doc

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Wilfrid Laurier University
Computer Science
Mark Petrick

Behind the Scenes: Databases and Info Systems Tuesday, February 05, 2013 3:29 PM Databases • Collection of information organized in a manner that allows for convenient retrieval • Examples that are non-computer databases: • Paper files, phone book, dictionary, day planner, sign-up sheet • terminology • Everything is stored in a 'table' (or files)  Group of related records • A 'record' is everything about the person (horizontal) A 'field' is a fact about the person (ex. the address field for 'Mark' contains the word "London")  Store each category of info in a column • All records have the same fields, just different data stored in those fields  Group of related rields • Fields are picky about what can be store in them (data types) Life without Databases: Lists • Lists are often sufficient for simple tasks • Not appropriate for complex info • Multiple lists lead to data redundancy, inconsistency, duplicate data, sorting issues, incomplete data • Not every situation demands complexity of a database • For simple tasks, lists are adequate • Table created in Microsoft Word • Spreadsheet created in Microsoft Excel • Lists are not appropriate for complex information Database Building Blocks • Data that needs organization and analysis can be put into a database • eBay keeps track of millions of items • Netflix stores subscriber information Advantages of Using Databases • Databases store and retrieve large quantities of info easily • Provide info in seconds • Three main advantages: • Enable info sharing, promote data integrity, allow flexible use of data • Using database lets data be centralized, only one copy of relevant data must be maintained • All database users therefore access the same up-to-date info Field Size • Defines max number of characters that field can hold • If you define field size of 50, space is reserved for 50 characters • Tailor field size to length of data it contains to avoid decreased performance Primary Keys • Each record must have one field that has value unique to that record • Unique field is called a primary key • Student ID numbers, social security numbers, driver's license numbers, unique order numbers Database Types • Three major types of databases in use: • Relational  Organize data in table format  Locally group similar data into relation (table that contains related data)  Each record is assigned primary key  Tables are linked to each other through their primary keys object-oriented •  Store data in objects  Also contain methods for processing or manipulating data  Can store more types of data than relational databases  Can access data faster • multidimensional  Store data in more than two dimensions  Organize data in cube format  Each data cube has a measures attribute: main type of data that cube is tracking  Other elements are feature attributes: describe measure attribute in meaningful way  Can be easily customized, process data faster • Relational databases have largest market share Database Management Systems • Databases are created and managed using database management system (DBMS) • Four main operations of DBMS: 1. Creating databases and entering data • Define data to be captured • Data dictionary or database schema (defines name, data type, length of each field) • Being creating individual records (key in directly or import data electronically) • For small databases, create input form to speed data entry 2. Viewing (or browsing) and sorting data View records by browsing or sort records by field name • 3. Querying (extracting) data • Inquiry; provides records you wish to view • Select and display records that match certain criteria • Query languages • Modern databases contain query language used to retrieve and display records • Most popular is structured query language (SQL), wizards speed up process of creating queries 4. Outputting data • Most common form of output is viewable (printable) electronic report • Summarize data and compile summary data reports • Export data to other applications • Put data into electronic file in format that another application can understand Data Validation • Validation: process of ensuring data entered into database is correct (or at least reasonable) and complete • Common times of validation checks: range, completeness, consistency, alphabetic/numeric Rational Database Operations • Organize data into various tables based on logical groupings • Methodology must be implemented to link data between tables Types of Relationships • One-to-one • For each record in table, there is only one corr
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