53425-计算机科学概论原书chapter

1、Chapter 12Information Systems2Chapter GoalsDefine the role of general information systemsExplain how spreadsheets are organizedCreate spreadsheets for basic analysis of dataDefine appropriate spreadsheet formulas using built-in functionsDesign spreadsheets to be flexible and extensibleDescribe the e

2、lements of a database management system3Chapter GoalsDescribe the organization of a relational databaseEstablish relationships among elements in a databaseWrite basic SQL statementsDescribe an entity-relationship diagramDefine and explain the role of merce in society today4Managing InformationInform

3、ation system Software that helps the user organize and analyze dataElectronic spreadsheets and database management systemsSoftware tools that allow the user to organize, manage, and analyze data in various waysHave you ever used a spreadsheet?5SpreadsheetsSpreadsheet A software application that allo

4、ws the user to organize and analyze data using a grid of labeled cellsA cell can contain data or a formula that is used to calculate a valueData stored in a cell can be text, numbers, or “special” data such as datesSpreadsheet cells are referenced by their row and column designationFigure 12.1 A spr

5、eadsheet, made up of a grid of labeled cells6SpreadsheetsSuppose we have collected data on the number of students that came to get help from a set of tutors over a period of several weeksFigure 12.1 A spreadsheet containing data and computations7Spreadsheet FormulasThe power of spreadsheets comes fr

6、om the formulas that we can create and store in cellsWhen a formula is stored in a cell, the result of the formula is displayed in the cellIf weve set up the spreadsheet correctly, we could add or remove tutors.add additional weeks of data.change any of the data we have already stored and the corres

7、ponding calculations would automatically be updated.8Spreadsheet FormulasFigure 12.3 The formulas behind some of the cells9Spreadsheet FormulasFormulas make use of basic arithmetic operations using the standard symbols (+, -, 2, *, and /)Spreadsheet functions Computations provided by the spreadsheet

8、 software that can be incorporated into formulas RangeA set of contiguous cells specified by the endpoints10Spreadsheet FormulasFigure 12.4 Some common spreadsheet functions11Circular ReferencesCircular reference A set of formulas that ultimately rely on each otherFigure 12.5 A circular reference si

9、tuation that cannot be resolvedCan you seethe circularreference?12Spreadsheet AnalysisCan you name eight tasks that a spreadsheet might be used to perform?Spreadsheet AnalysisPossible tasks a spreadsheet could perform:Track salesAnalyze sport statisticsMaintain student gradesKeep a car maintenance l

10、ogRecord and summarize travel expensesTrack project activities and schedulesPlan stock purchases1314Spreadsheet AnalysisSpreadsheets are also useful because of their dynamic nature, which provides the powerful ability to do what-if analysisWhat if the number of attendees decreased by 10%?What if we

11、increase the ticket price by $5?What if we could reduce the cost of materials by half?15Database Management SystemsDatabase A structured set of dataDatabase management system (DBMS) A combination of software and data, made up of a physical database, a database engine, and a database schemaPhysical d

12、atabase A collection of files that contain the data16Database Management SystemsDatabase engine Software that supports access to and modification of the database contentsDatabase schema A specification of the logical structure of the data stored in the databaseDatabase queryA request to retrieve dat

13、a from a database17Database Management SystemsFigure 12.6 The elements of a database management system18The Relational ModelRelational DBMS A DBMS in which the data items and the relationships among them are organized into tablesTables A collection of recordsRecords (object, entity)A collection of r

14、elated fields that make up a single database entryFields (attributes)A single value in a database record19A Database TableFigure 12.7 A database table, made up of records and fieldsHow do weuniquelyidentify arecord?20A Database TableKeyOne or more fields of a database record that uniquely identifies

15、 it among all other records in the tableWe can express the schema for this part of the database as follows:Movie (MovieId:key, Title, Genre, Rating)21A Database TableFigure 12.8 A database table containing customer data22RelationshipsHow do we relate movies to customers?By a table, of course!Figure

16、12.9 A database table storing current movie rentalsWho isrentingwhatmovie?23Structured Query LanguageStructured Query Language (SQL) A comprehensive relational database language for data manipulation and queriesselect attribute-list from table-list where conditionname of field name of table value re

17、strictionselect Title from Movie where Rating = PGResult is a table containing all PG movies in table Movie24Queries in SQL select Name, Address from Customerselect * from Movie where Genre like %action%select * from Movie where Rating = R order by TitleWhat does each of these queries return?25Modif

18、ying Database Contentinsert into Customer values (9876, John Smith, 602 Greenbriar Court, 2938 3212 3402 0299)update Movie set Genre = thriller drama where title = Unbreakabledelete from Movie where Rating = RWhat does each of these statements do?26Database DesignEntity-relationship (ER) modeling A

19、popular technique for designing relational databasesER Diagram A graphical representation of an ER modelCardinality constraintThe number of relationships that may exist at one time among entities in an ER diagram27Database DesignFigure 12.10 An ER diagram for the movie rental databaseHow many movies can a person rent?How many people can rent the same movie?28 merceElectronic commerceThe process of buying and selling products and services using the Web.Can you name at least 4 merce sitesthat you have visited lately?What made merce feasible and easy?