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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
Contents
• Computer Databases
• Database Management Systems
• The DBMS Process
• Concurrency Control
• Security
• Backup and Recovery
• Looking at the Data
Computer Databases
• Track information
• Keep consistent standards
• Allow higher productivity as a result of better information
Hierarchy of Data
• Field– Smallest meaningful unit of data– Group of one or more characters that has a
specific meaning
• 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
File Processing
• File processing– Data redundancy
• Database models reduce redundancy– Saves storage space– Saves update effort
• Time• Accuracy
Database Models
• Database Types– Relational– Object-oriented– Hierarchical– Network
• Each type structures, organizes and uses data differently
RDBMSRelational Database Management System
• Organizes data into related tables (files)
• Table consists of rows and columns
• Tables linked based upon a common field (key)
RDBMSKey
• 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
OODBMSObject-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
OODBMSObject-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
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
DBMSDatabase 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
DBMSDatabase Management System
Basic functions
• Create a database
• Enter data
• Modify the data as required
• Retrieve information from the database
DBMSCreate 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
DBMSEnter 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
DBMSData Retrieval
• Extracting the desired data from the database
• Primary forms– Queries– Reports
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
Query
SQLStructured Query Language
Entered directly by userIncluded in programs
QBEQuery-by-Example
Graphical interface to specify your criteria
Report
• Formatted presentation of data from the database
• Normally printed
• Designed using a report generator
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
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
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
Looking at the DataOLTP – Online Transaction Processing
• Supports day-to-day database activities
• Little support for data analysis
Looking at the DataData Warehouses
• Databases designed to support ongoing operations
• Data is captured from the db– Summary form– Scheduled basis– Period of time
• May include data from external sources
Looking at the DataData Warehouses
• Online Analytical Processing (OLAP)– Analyzes the data– Produces information for managers
• Data mining– Statistical and artificial intelligence techniques– Look for unrecognized
• Patterns• Relationships• Correlations• Trends
– Helps managers make strategic business decisions
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