chapter 12: databases and database management systems

In-memory databases (IMDBs)

(main memory databases (MMDBs)) - All data is stored in main memory - Use is growing as memory costs fall - Dramatically faster than disk-based databases - Good backup procedures are essential because RAM is volatile - Used both in high-end systems where performance is crucial and in small-footprint, embedded applications

Distributed database system

- Data is physically divided among several computers connected by a network, but appears as a single database to users - Allows data to be stored at the site where it is needed most frequently or that makes data retrieval most efficient - Cloud databases

Multiuser database system

- Designed to be accessed by multiple users (most business databases today)

Single-user database system

- Located on a single computer - Designed to be accessed by one user - Widely used for personal applications and very small businesses

Direct organization

- Uses hashing algorithms to specify the exact storage location - Algorithms should be designed to limit collisions

Records (rows)

Collection of related fields in a database (all the fields for one customer, for example)

Centralized database system

Database is located on a single computer, such as a server or mainframe

form

New data can be added using the table's Datasheet view

Fields (columns)

Single category of data to be stored in a database (name, telephone number, etc.)

Indexed organization

Uses an index to keep track of where data is stored in a database

Object-oriented database management system (OODBMS)

a database system in which multiple types of data are stored as objects along with their related code - Can contain virtually any type of data (video clip, text with music, etc.) along with the methods to be used with that data - Objects can be retrieved using queries (object query language or OQL) - Objects can be reused in other applications to create new applications quickly

Cloud databases

accessible to users via the Web - Used in conjunction with businesses Web sites to display product information, facilitate online ordering, etc. - Used to facilitate searching for information - Store user-generated content (Flickr, YouTube, Facebook, etc.) - Allow Web pages to be dynamic Web pages

Data privacy

addresses protecting the privacy of personal data stored in databases - Many states require businesses to notify customers when their personal data has been compromised - Data breaches can be costly • One estimate is $200 per breached record - To protect the privacy of data, businesses should: • Make sure all data they are collecting and storing is necessary • Make sure they use adequate security measures

Multidimensional databases (MDDB)

are designed to be used with data warehousing - Designed to store a collection of summarized data for quick and easy data analysis - Data is collected from a variety of activities and then summarized and restructured to be viewed from multiple perspectives (dimensions) - One of the most common types of software used is Online Analytical Processing (OLAP)

Hybrid XML/relational databases

can store and retrieve both XML data and relational data - DB2

structured query language (SQL)

can write a query

Middleware

connects the Web server and the database • Commonly written as scripts - CGI scripts are written in programming languages (C, Perl, Java, etc.) - Active Server Pages (ASPs) are written in JavaScript or VBScript • PHP scripts use PHP tags inserted into the Web page HTML

data dictionary

contains all data definitions in a database - Table structures - Security information (passwords, etc.) - Relationships between the tables in the database - Basic information about each table (e.g., # of records) • Does not contain any of the data in the tables - Ensures that data being entered into the database does not violate any of its assigned properties

relational database management system (RDBMS)

data is organized in tables related by common fields

Reports

formatted way of looking at a database table or the results of a query - Can pull data from more than one table (if related) - Many programs have wizards or other tools to make it easy to create a report - In Access, reports are often created using the Report Wizard and then modified as needed using the report's Design view - Reports in Microsoft Access are saved as objects in the database file - When a report is opened, the current data is displayed in the specified format

client-server database system

has both clients (front end) and at least one database server (back end)

metadata

information about the database tables

attribute

is a characteristic of an entity - Typically become fields in the entity's database table

database

is a collection of related data stored in a manner that enables information to be retrieved as needed

primary key

is a field that uniquely identifies the records in a table - Used in a relational database to relate that table to other tables

entity

is a person, object, or event of importance to the organization - Entities that the organization wants to store data about typically becomes a database table

query

is a request to see information from a database that matches specific criteria - In Access, can create a query object that specifies what fields and records should be displayed - Each time a query is run, the data currently meeting the specified conditions is displayed - Must be designed to extract information as efficiently as possible - Poorly written queries can impact the overall performance of the system

Data definition

is the process of describing the properties of data 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, Yes/No, etc.) • Description (optional description of the field) • Properties (field size, format of the field, allowable range, if field is required, initial value, etc.) - Finished specifications for a table become the table structure

database management system (DBMS)

is the software used to create, maintain, and access databases - Database engine is the part of the program that actually stores and retrieves data - Most DBMSs also come bundled with a set of tools to perform a variety of necessary tasks

redundancy

normalization

Data security

protects data against destruction and misuse (both intentional and accidental) - Protects against unauthorized access to and unauthorized use of a database and data loss • Firewalls, access controls, access privileges, etc. - Database activity monitoring programs can be used to detect possible intrusions and risks - Database encryption should be used - Strict backup and disaster-recovery procedures can protect against data loss due to database failure, accidental deletions, disasters, etc.

Data integrity

refers to the accuracy of data - Quality of data entered determines the quality of generated information

Data validation

refers to the process of ensuring that data entered into the database is valid - Ensures entered data matches the specified data type, format, and allowable value for each field - Can include record validation rules (checking the value of a field with the value of another field to ensure validity) - If data is invalid, an error message is usually displayed - Can be enforced on a per transaction basis so that the entire transaction will fail if one part is invalid

Tables

• Collection of related records • Are often interrelated with other tables in the database