Intro To Database systems

Extensible Markup Language (XML)

A metalanguage used to represent and manipulate data elements. Unlike other markup languages, XML permits the manipulation of a document's data elements.

Data Managment

A process that focuses on data collection, storage, and retrieval. Common data management functions include addition, deletion, modification, and listing

Database

A shared, integrated computer structure that houses a collection of related data. A database contains two types of data: end-user data (raw facts) and metadata.

Database Requirements

Both centralized and decentralized (distributed) databases require a well-defined infrastructure (hardware, operating systems, network technologies, etc.) to implement and operate the database. Typically, the infrastructure is owned and maintained by the organization that creates and operates the database. But in recent years, the use of cloud databases has been growing in popularity.

Metadata

Data about data; that is, data about data characteristics and relationships. See also data dictionary For example, the metadata component stores information such as the name of each data element, the type of values (numeric, dates, or text) stored on each data element, and whether the data element can be left empty. In short, metadata presents a more complete picture of the data in the database. Given the characteristics of metadata, you might hear a database described as a "collection of self-describing dat

Basic file terminology

Field A character or group of characters (alphabetic or numeric) that has a specific meaning. A field is used to define and store data. Record A logically connected set of one or more fields that describes a person, place, or thing. File A collection of related records. For example, a file might contain data about the students currently enrolled at Gigantic University

database management systems provide these advantages

Improved data sharing. The DBMS helps create an environment in which end users have better access to more and better-managed data. Such access makes it possible for end users to respond quickly to changes in their environment. • Improved data security. The more users access the data, the greater the risks of data security breaches. Corporations invest considerable amounts of time, effort, and money to ensure that corporate data is used properly. A DBMS provides a framework for better enforcement of data privacy and security policies. • Better data integration. Wider access to well-managed data promotes an integrated view of the organization's operations and a clearer view of the big picture. It becomes much easier to see how actions in one segment of the company affect other segments . • Minimized data inconsistency. Data inconsistency exists when different versions of the same data appear in different places. For example, data inconsistency exists when a company's sales department stores a sales representative's name as Bill Brown and the company's personnel department stores that same person's name as William G. Brown, or when the company's regional sales office shows the price of a product as $45.95 and its national sales office shows the same product's price as $43.95. The probability of data inconsistency is greatly reduced in a properly designed database. • Improved data access. The DBMS makes it possible to produce quick answers to ad hoc queries. From a database perspective, a query is a specific request issued to the DBMS for data manipulation—for example, to read or update the data. Simply put, a query is a question, and an ad hoc query is a spur-of-the-moment question. The DBMS sends back an answer (called the query result set) to the application. For example, when dealing with large amounts of sales data, end users might want quick answers to questions (ad hoc queries). Some examples are the following: - What was the dollar volume of sales by product during the past six months? - What is the sales bonus figure for each of our salespeople during the past three months? - How many of our customers have credit balances of $3,000 or more? • Improved decision making. Better-managed data and improved data access make it possible to generate better-quality information, on which better decisions are based. The quality of the information generated depends on the quality of the underlying data. Data quality is a comprehensive approach to promoting the accuracy, validity, and timeliness of the data. While the DBMS does not guarantee data quality, it provides a framework to facilitate data quality initiatives. Data quality concepts will be covered in more detail in Chapter 16, Database Administration and Security. • Increased end-user productivity. The availability of data, combined with the tools that transform data into usable information, empowers end users to make quick, informed decisions that can make the difference between success and failure in the global economy

Evolution of File System Data Processing

Manual File Systems -> Computerized File Systems -> File System Redux: Modern End User Productivity Tools

Data

Raw facts, or facts that have not yet been processed to reveal their meaning to the end user.

Structural dependence Structural independence Data type Data dependence Data independence Logical Data Format Physical Data format

Structural dependence A data characteristic in which a change in the database schema affects data access, thus requiring changes in all access programs. Structural independence A data characteristic in which changes in the database schema do not affect data access. Data type Defines the kind of values that can be used or stored. Also, used in programming languages and database systems to determine the operations that can be applied to such data. Data dependence A data condition in which data representation and manipulation are dependent on the physical data storage characteristics. Data independence A condition in which data access is unaffected by changes in the physical data storage characteristics. Logical data format The way a person views data within the context of a problem domain. Physical data format The way a computer "sees" (stores) data.

database management system (DBMS)

The collection of programs that manages the database structure and controls access to the data stored in the database The DBMS receives all application requests and translates them into the complex operations required to fulfill those requests. The DBMS hides much of the database's internal complexity from the application programs and users. Having a DBMS between the end user's applications and the database offers some important advantages. First, the DBMS enables the data in the database to be shared among multiple applications or users. Second, the DBMS integrates the many different users' views of the data into a single all-encompassing data repository

Problems with file system data processing

The following problems associated with file systems, whether created by DP specialists or through a series of spreadsheets, severely challenge the types of information that can be created from the data as well as the accuracy of the information: • Lengthy development times. The first and most glaring problem with the file system approach is that even the simplest data-retrieval task requires extensive programming. With the older file systems, programmers had to specify what must be done and how to do it. As you will learn in upcoming chapters, modern databases use a nonprocedural data manipulation language that allows the user to specify what must be done without specifying how. • Difficulty of getting quick answers. The need to write programs to produce even the simplest reports makes ad hoc queries impossible. Harried DP specialists who worked with mature file systems often received numerous requests for new reports. They were often forced to say that the report will be ready "next week" or even "next month." If you need the information now, getting it next week or next month will not serve your information needs. • Complex system administration. System administration becomes more difficult as the number of files in the system expands. Even a simple file system with a few files requires creating and maintaining several file management programs. Each file must have its own file management programs that allow the user to add, modify, and delete records; to list the file contents; and to generate reports. Because ad hoc queries are not possible, the file reporting programs can multiply quickly. The problem is compounded by the fact that each department in the organization "owns" its data by creating its own files. • Lack of security and limited data sharing. Another fault of a file system data repository is a lack of security and limited data sharing. Data sharing and security are closely related. Sharing data among multiple geographically dispersed users introduces a lot of security risks. In terms of spreadsheet data, while many spreadsheet programs provide rudimentary security options, they are not always used, and even when they are, they are insufficient for robust data sharing among users. In terms of creating data management and reporting programs, security and data-sharing features are difficult to program and consequently are often omitted from a file system environment. Such features include effective password protection, the ability to lock out parts of files or parts of the system itself, and other measures designed to safeguard data confidentiality. Even when an attempt is made to improve system and data security, the security devices tend to be limited in scope and effectiveness. • Extensive programming. Making changes to an existing file structure can be difficult in a file system environment. For example, changing just one field in the original CUSTOMER file would require a program that: 1. reads a record from the original file 2. transforms the original data to conform to the new structure's storage requirements 3. writes the transformed data into the new file structure 4. repeats the preceding steps for each record in the original file. In fact, any change to a file structure, no matter how minor, forces modifications in all of the programs that use the data in that file. Modifications are likely to produce errors (bugs), and additional time is spent using a debugging process to find those errors. Those limitations, in turn, lead to problems of structural and data dependence

data processing (DP) specialist

The person responsible for developing and managing a computerized file processing system.

Information

The result of processing raw data to reveal its meaning. Information consists of transformed data and facilitates decision making. To reveal meaning, information requires context

XML database, social media, NoSQL, database design

XML database A database system that stores and manages semistructured XML data. social media Web and mobile technologies that enable "anywhere, anytime, always on" human interactions. NoSQL A new generation of DBMS that is not based on the traditional relational database model. database design The process that yields the description of the database structure and determines the database components. The second phase of the database life cycle.

Types of Databases

databases can be classified by the number of users supported, where the data is located, the type of data stored, the intended data usage, and the degree to which the data is structured. • single-user database A database that supports only one user at a time. desktop database A single-user database that runs on a personal computer. • multiuser database A database that supports multiple concurrent users. • workgroup database A multiuser database that usually supports fewer than 50 users or is used for a specific department in an organization. • enterprise database The overall company data representation, which provides support for present and expected future needs. centralized database A database located at a single site. • distributed database A logically related database that is stored in two or more physically independent sites. • cloud database A database that is created and maintained using cloud services, such as Microsoft Azure or Amazon AWS. • general-purpose database A database that contains a wide variety of data used in multiple disciplines. • discipline-specific database A database that contains data focused on specific subject areas.

Chapter 1 Summary

• Data consists of raw facts. Information is the result of processing data to reveal its meaning. Accurate, relevant, and timely information is the key to good decision making, and good decision making is the key to organizational survival in a global environment. • Data is usually stored in a database. To implement a database and to manage its contents, you need a database management system (DBMS). The DBMS serves as the intermediary between the user and the database. The database contains the data you have collected and "data about data," known as metadata. • Database design defines the database structure. A well-designed database facilitates data management and generates accurate and valuable information. A poorly designed database can lead to poor decision making, and poor decision making can lead to the failure of an organization. • Databases can be classified according to the number of users supported, where the data is located, the type of data stored, the intended data usage, and the degree to which the data is structured. • Databases evolved from manual and then computerized file systems. In a file system, data is stored in independent files, each requiring its own data management programs. Although this method of data management is largely outmoded, understanding its characteristics makes database design easier to comprehend. • Some limitations of file system data management are that it requires extensive programming, system administration can be complex and difficult, making changes to existing structures is difficult, and security features are likely to be inadequate. Also, independent files tend to contain redundant data, leading to problems of structural and data dependence. • DBMSs were developed to address the file system's inherent weaknesses. Rather than depositing data in independent files, a DBMS presents the database to the end user as a single data repository. This arrangement promotes data sharing, thus eliminating the potential problem of islands of information. In addition, the DBMS enforces data integrity, eliminates redundancy, and promotes data security. • Knowledge of database technologies leads to many career opportunities in the ever-expanding IT industry. There is a variety of specialization within the database arena for a wide range of skills and expertise

Key Points

• Data constitutes the building blocks of information. • Information is produced by processing data. • Information is used to reveal the meaning of data. • Accurate, relevant, and timely information is the key to good decision making. • Good decision making is the key to organizational survival in a global environment. The processing of data is used to reveal information that in turn generates "actionable" knowledge

More databases

• operational database A database designed primarily to support a company's day-to-day operations. Also known as a transactional database, • OLTP database, or production database. online transaction processing (OLTP) database See operational database. • transactional database See operational database. • production database See operational database. • analytical database A database focused primarily on storing historical data and business metrics used for tactical or strategic decision making. • data warehouse A specialized database that stores historical and aggregated data in a format optimized for decision support. • online analytical processing (OLAP) A set of tools that provide advanced data analysis for retrieving, processing, and modeling data from the data warehouse. • business intelligence A set of tools and processes used to capture, collect, integrate, store, and analyze data to support business decision making. • unstructured data Data that exists in its original, raw state; that is, in the format in which it was collected • structured data Data that has been formatted to facilitate storage, use, and information generation. • semi-structured data Data that has already been processed to some extent.