Database Management: Getting Data Together Chapter 14

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

Hierarchy of Data

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

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)

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

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

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

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

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

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

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

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

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

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

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

The DBMS Process The Plan… The Report…

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

Concurrency Control

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 Data OLTP – Online Transaction Processing Supports day-to-day database activities Little support for data analysis

Looking at the Data Data 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 Data Data 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