Welcome to CMPE003 Personal Computers: Hardware and Software Dr. Chane Fullmer Fall 2002 UC Santa Cruz

November 18, Exams Exams now on-line….. Must have your own Scantron form to determine test version you took

November 18, Assignments Assignment #6 – The Last One Due November 22, 2002 This Friday…don’t be late.. Using Spreadsheets – (M$ Excel) Generate a personal monthly budget spreadsheet Must printout in color if you use color for the conditional in part #10

Database Management: Getting Data Together Chapter 14

November 18, Objectives Describe the hierarchy of data Explain the differences between files and databases List the four database models Describe the concept of data integrity Describe the functions of a database management system Describe the process of creating a database in general terms Compare and contrast relational and object-oriented databases Explain what a data warehouse is an how it differs from a database

November 18, Computer Databases Track information Allows higher productivity as a result of better information

November 18, Hierarchy of Data Field Smallest meaningful unit of data Group of one or more characters that has a specific meaning Used as “key” to locate records Record Set of fields containing all information known about one entity Each record contains the same fields in the same sequence File Collection of related records

November 18, Hierarchy of Data

November 18, File Processing File processing Data redundancy Database models reduce redundancy Saves storage space Saves update effort Time Accuracy

November 18, Data (From Chapter 6) Organizing and Accessing Design (plan) for way data is Received Organized Stored how it will be processed Plan determined by programmer and/or systems analyst

November 18, Data Getting Organized Character Field Record File Database

November 18, Data Access Methods Application determines how data must be accessed by users Data is organized based upon access method Organization method limits choice of storage medium

November 18, Sequential Records are stored and accessed in order All records prior to the one requested must be read Magnetic tape storage

November 18, Direct / Random Access Records are not physically stored in any order Go directly to the record to read Hashing – apply a formula to the key to produce the address of the record Collision – same address from different keys Updating in place Read, change, and return a record to the same place on disk DASD – Direct-Access Storage Device needed ie, Disk Drive

November 18, Indexed Records are stored sequentially Index is generated that contains key and address Can be read in order = sequential Can be read out of order = random

November 18, Processing Stored Data Batch Transaction Terminology Transaction – updates a record Master file – contains all the data

November 18, Batch Processing Collect transactions into a transaction file and perform periodic updates Process Transactions are sorted by key field Computer matches the master and transaction keys Performs requested action – add, revise, delete New master file created Error report is printed Master file only current immediately after processing

November 18, Batch Processing Stored Data

November 18, Transaction Processing Processed upon request Real-time – process handled immediately Disk storage Direct access to desired record needed Immediate access to stored data Immediate updating of stored data

November 18, Batch and Transaction Computer system may use both processing types based upon the application Transaction Activities relating to current needs Batch Updates per schedule

November 18, Applications Motor Vehicle Dept Transaction Police check for stolen car report Batch Motor vehicle records of owner information Retail – POS Transaction Item price Inventory updates as sale is made Batch Produce daily and weekly sales reports Banks Transaction Check balance Record cash withdrawal Batch Deposit left in the deposit drop Bank statement

November 18, Database Models Database Types Relational Object-oriented Hierarchical Network Each type structures, organizes and uses data differently

November 18, RDBMS Relational Database Management System Organizes data into related tables (files) Table consists of rows and columns Tables linked based upon a common field (key)

November 18, RDBMS Key Primary key A field whose value uniquely identifies a record Foreign key Primary key of another table Used as link to other table May have duplicate values

November 18, OODBMS Object-Oriented Database Management System Manipulates object-oriented databases Object – represents a real-world entity Attributes / properties Data about the entity Methods / Actions Operations that work the data

November 18, OODBMS Object-Oriented Database Management System Compared to RDBMS More complex Steeper learning curve Skilled employees needed who earn high pay Combined Object/relational DBMS Relational database that incorporates some complex data types

November 18, Data Integrity Degree to which data is accurate and reliable Integrity constraints – rules Acceptable values for a field Primary key values Foreign keys Integrity constraints must be enforced when data is entered or data is unreliable GIGO (Garbage in, garbage out)

November 18, DBMS Database Management System Levels of software Sophisticated Mainframe Expensive – tens of thousands of dollars Complex Planned and managed by computer professionals Simple PC Inexpensive – few hundred dollars User can set up and use the database

November 18, DBMS Database Management System Basic functions Create a database Enter data Modify the data as required Retrieve information from the database

November 18, DBMS Create a Database Data Dictionary / Catalog Stored data about the tables and fields within the database Per table Table name Relationships Per field Field name Data type Field size Validation rules

November 18, DBMS Enter and Modify Data Operations Adding new data Modifying data Deleting data Methods User interacts directly with DBMS Programs written by professional programmers access the data using special commands built into the DBMS

November 18, DBMS Data Retrieval Extracting the desired data from the database Primary forms Queries Reports

November 18, Query Ask a question about the data Present criteria that selects data from the database Results in smaller portion of the database Query Language Prepare your query using English-like statements Proprietary query language in DBMS

November 18, Query SQL Structured Query Language Entered directly by user Included in programs QBE Query-by-Example Graphical interface to specify your criteria

November 18, Report Formatted presentation of data from the database Normally printed Designed using a report generator

November 18, The DBMS Process Enter the data Review the data and edit until accurate Describe the data

November 18, The DBMS Process The Plan… The Report…

November 18, Concurrency Control Databases are used concurrently by many users Problem if several users attempt to update the same record at the same time Record locking First user requests record Others are locked out for update

November 18, Concurrency Control

November 18, Security Data is stored in a central location Problem: unauthorized access is major concern Benefit: easier to apply security measures Features User ID and password Privileges assigned to each user Read-only Update

November 18, Backup and Recovery Why? Data can be accidentally damaged or destroyed Hardware can fail Forces of nature can cause physical damage Software or human errors can corrupt data Backup – copy made periodically Recovery – replaces the damaged database with the good backup

November 18, Looking at the Data OLTP – Online Transaction Processing Supports day-to-day database activities Little support for data analysis

November 18, Looking at the Data Data Warehouses Databases designed to support ongoing operations Data is captured from the db over time Summary form Scheduled basis Period of time May include data from external sources

November 18, Looking at the Data Data Warehouses Online Analytical Processing (OLAP) Analyzes the data Produces information for managers Data mining Statistical and artificial intelligence techniques Look for otherwise unrecognized -- Patterns Relationships Correlations Trends Helps managers make strategic business decisions

November 18,