Databases and Database Management Systems

11th Edition TODAY AND TOMORROW Databases and Database Management Systems • 14 CHAPTER Chapter 14 Understanding Computers, 11th Edition

Learning Objectives • Explain what a database is, including common database terminology, and list some of the advantages and disadvantages of using databases. • Discuss some basic concepts and characteristics of data, such as data hierarchy, entity relationships, data definition, and organization. • Describe the importance of data integrity, security, and privacy and how it affects database design. Chapter 14 Understanding Computers, 11th Edition

Learning Objectives, Cont’d • Identify some basic database classifications and discuss their differences. • List the most common database models and discuss how they are used today. • Understand how a relational database is designed, created, used, and maintained. • Describe some ways databases are used on the Web. Chapter 14 Understanding Computers, 11th Edition

Overview • This chapter covers: • What databases are and advantages for using them • Database concepts and vocabulary • Key characteristics about the data in a database • Database classifications and models • The relational database model • How databases are used on the Web Chapter 14 Understanding Computers, 11th Edition

What Is a Database? • Database: a collection of related data stored in a manner so it can be retrieved as needed • Database management system (DBMS): used to create, maintain, and access computer databases • A database typically consists of: • Tables: in a relational database, a collection of related records • Fields (columns): single category of data to be stored in a database • Records (rows): collection of related fields in a database Chapter 14 Understanding Computers, 11th Edition

Relational Databases: A Simple Example • In a relational database, data from several tables is tied together (related ) using a field that the tables have in common • Primary key: specific field in a database table that uniquely identifies the records in that table • DBMSs available for use on PCs include • Microsoft Access (most widely used) • Corel Paradox • Lotus Approach • For more comprehensive enterprise databases • Oracle • IBM DB2 Chapter 14 Understanding Computers, 11th Edition

Chapter 14 Understanding Computers, 11th Edition

Individuals Involved With a Database Management System • Users: use an interface to enter data, update data, and pull information out of the database • Database designers: design the database • Database developers: create the database • Database programmers: write the programs needed to access the database or tie the database to other programs • Database administrators: responsible for managing the large databases found within an organization Chapter 14 Understanding Computers, 11th Edition

The Evolution of Databases Chapter 14 Understanding Computers, 11th Edition

Advantages and Disadvantages of the Database Approach • Advantages • Better information • Faster response time • Lower operating costs and storage requirements • Improved data integrity and better data management • Disadvantages • Higher software cost • Increased vulnerability (backup is essential) Chapter 14 Understanding Computers, 11th Edition

Data Concepts and Characteristics • Data in a database has a certain hierarchy • Characters • Fields/columns (hold single pieces of data) • Records/rows (groups of related fields) • Tables (collection of related records) • Database (contains a group of related tables) Chapter 14 Understanding Computers, 11th Edition

Data Concepts and Characteristics, Cont’d • Entity: something of importance to the organization • Entities that the organization wants to store data about typically becomes a database table Relationships • Attributes: characteristics of entities • Attributes typically become fields in the entity’s database table • Entity relationships • One-to-one (1:1) entity relationships • One-to-many (O:M) entity relationships • Many-to-many (M:M) entity relationships Chapter 14 Understanding Computers, 11th Edition

Data Concepts and Characteristics, Cont’d • Datadefinition: process of describing the characteristics of data that is to be included in a database table • During data definition, each field is assigned: • Name (must be unique within the table) • Data type (such as Text, Number, Currency, or Date) • Properties (field size, format of the field, allowable range, input mask, etc.) • Finished specifications for a table become the table structure Chapter 14 Understanding Computers, 11th Edition

Data Dictionary • Datadictionary: repository of all data definitions in a database • Includes data about the data in the tables (metadata), such as: • Table structures • Security information (passwords, etc.) • Relationships between the tables in the database • Current information about each table, such as the current number of records • Ensures that data being entered into the database does not violate any specified criteria Chapter 14 Understanding Computers, 11th Edition

Data Integrity, Security, and Privacy • Data integrity: the accuracy of data • Quality of data input determines the quality of retrieved information (GIGO) • Data validation: ensuring that data entered into the database matches the data definition • Helps to increase data integrity • Can be enforced on a per transaction basis so the entire transaction will fail if one part is invalid • Database locking: prevents two individuals from changing the same data at the same time Chapter 14 Understanding Computers, 11th Edition

Data Integrity, Security, and Privacy, Cont’d • Data security: protecting data against destruction and misuse • Prevents access from unauthorized individuals • Protects against data loss • Protects against both intentional and unintentional problems • Should include strict backup and disaster-recovery procedures (disaster-recovery plan) • Data privacy: growing concern because of the vast amounts of personal data stored in databases today Chapter 14 Understanding Computers, 11th Edition

Data Organization • Data organization: arranging data for efficient retrieval • Indexedorganization: uses an index to keep track of where data is stored • Index: small table containing a primary key and the location of the record belonging to that key • Direct organization: uses hashing to specify the exact storage location Chapter 14 Understanding Computers, 11th Edition

Database Classifications • Single-user database systems: designed to be accessed by one user • Multiuser database systems: designed to be accessed by multiple users (most business databases today) • Client-server database systems: has both clients and at least one server Chapter 14 Understanding Computers, 11th Edition

Database Classifications, Cont’d • N-tier database systems: have more than two tiers • Middle tiers contain one or more programs stored on one or more computers • Centralized database systems: Database is located on a single computer, such as a server or mainframe • Distributed database systems: Data is physically divided among several computers connected by a network, but the database logically looks like it is a single database • In-memory databases (IMDBs): Data is stored in main memory, instead of on disk Chapter 14 Understanding Computers, 11th Edition

Database Models • Two older models are: • Hierarchical databases:store data in the form of a tree, with typically a one-to-many relationship between data entities • Network databases:the relationship between data elements is usually either one-to-many or many-to-many Chapter 14 Understanding Computers, 11th Edition

The Relational Database Model • Relational database management system (RDBMS): data is stored in tables related by common fields; the most widely used database model today Chapter 14 Understanding Computers, 11th Edition

The Relational Database Model, Cont’d • Properly designing a relational database before creating it is important Chapter 14 Understanding Computers, 11th Edition

The Relational Database Model, Cont’d • To create a relational database: • Create the structure of each individual table • Enter data using a created form or the regular Datasheet view • Migrate any existing data to the new database • Modify tables, if needed, using the Design view • Relate tables as needed Chapter 14 Understanding Computers, 11th Edition

The Relational Database Model, Cont’d • To retrieve information from a relational database, can use a: • Query: arequest to see information from a database that matches specific criteria • Often written in structured query language (SQL) • Many programs have wizards or other tools to make it easy to create a query • Can specify the fields to be displayed • Specify which records should be retrieved by specifying criteria Chapter 14 Understanding Computers, 11th Edition

The Relational Database Model, Cont’d • To retrieve information from a relational database, can use a: • Report: formatted means of looking at a database table or the results of a query • Reports can pull data from more than one table • Includes headings, formatting, etc. • Many programs have wizards or other tools to make it easy to create a report • Both reports and queries are saved so they can be retrieved again when needed Chapter 14 Understanding Computers, 11th Edition

Relational Database Model, Cont’d • Relational databases typically require ongoing maintenance, including: • Modifying the table structure when needed • Adding new indexes to speed up queries • Deleting obsolete data • Upgrading database software, installing patches • Repairing/restoring data that has become corrupt • Continuing to evaluate and improve security Chapter 14 Understanding Computers, 11th Edition

The Object-Oriented Database Model • Object-oriented database management system (OODBMS): a type of database system in which multiple types of data are stored as objects along with their related code • Objects consist of related attributes stored with methods associated with the object, similar to object-oriented programs • Objects in an OODBMS can contain virtually any type of data—video clip, photograph with a narrative, text with music, and so on—along with its related code • Object-relational database management systems (ORDBMS) also exist Chapter 14 Understanding Computers, 11th Edition

Multidimensional Databases • Multidimensional database (MDDB): a type of database in which data can be viewed from multiple dimensions or perspectives • Commonly used with data warehousing • Often used in conjunction with: Online Analytical Processing (OLAP) • MOLAP (Multidimensional OLAP): data stored in single structures called data cubes • ROLAP (Relational OLAP): information stored in an existing relational database using tables to store the summary information • HOLAP (Hybrid OLAP): combination of MOLAP and ROLAP technologies Chapter 14 Understanding Computers, 11th Edition

Databases and the Web • Databases are commonly used on the Web, such as for: • Information retrieval • Dynamic Web pages (change based on user input) • E-commerce Chapter 14 Understanding Computers, 11th Edition

Databases and the Web, Cont’d • Requests to retrieve or store information from or in a Web database is typically initiated by the Web site visitor • Web server converts the request into a database query and passes it onto the database server, and then sends the results back to the visitor • Middleware is used to connect two otherwise separate applications, such as a Web server and a database management system • CGI (common gateway interface) • API (application interface) • PHP (PHP Hypertext Preprocessor) Chapter 14 Understanding Computers, 11th Edition

Summary • What Is a Database? • Data Concepts and Characteristics • Database Classifications • Database Models • Databases and the Web Chapter 14 Understanding Computers, 11th Edition

Databases and Database Management Systems