Introduction to Databases

Objectives

• This chapter introduces the differences between data and information.
• An overview of what databases are will be covered, as well as different database types, and their value for decision-making.
• This chapter will explain the importance of database design, and how databases evolved from file systems.
• You will also learn about the flaws in file system data management.
• The main components of a database system will also be covered.
• The main functions of a Database Management System (DBMS) will be explained.

Introduction

• Good decisions require good information that is derived from raw facts.
• Data is managed most efficiently when it is stored in a database.
• Databases evolved from computer file systems.
• Understanding file system characteristics is important for database design.

Why Databases

• Databases solve data management related problems in modern settings.
• It is important to understand how databases work and interact with other applications in business, research and administration.

Data vs Information

• Data are raw facts, and information is the result of processing raw data; it gives the data meaning.
• Information requires context to reveal its meaning.
• Raw data must be formatted for storage, processing, and presentation.
• Data serves as the base for information, which is the bedrock of knowledge.
• Data is the building blocks, whereas information is what the data creates.
• Accurate, relevant, and timely information are key for good decision making,
• Good decions are key to the survival of an organizations.
• Data management focuses on proper generation, storage, and retrieval of data.

Introducing the Database

• A database is a shared, integrated computer structure that stores a collection of data.
• End-user data is a raw fact of interest to the end user.
• Metadata is data about data, and provides descriptions of data characteristics and the relationships in the data; it complements and expands the value of the data.
• A Database Management System (DBMS) is a collection of programs that manages the database structure and controls access to the data.

Role and Advantages of the DBMS

• The DBMS exists between the user and the database, with the database structure being stored as a collection of files.
• Files can only be accessed through the DBMS.
• The DBMS enables data to be shared and it integrates many users' views of the data.
• The advantages of a DBMS includes; improved data sharing and security, better data integration, minimised data inconsistency, improved data access and decision making, and increased end-user productivity.

Types of Databases

• Databases are classified based on the number of users, database location(s), or the expected type and extent of use.
• Single-user databases supports one user at a time, such as a desktop database, which is single-user database that runs on a PC.
• Multiuser database supports multiple users at the same time, such as workgroup and enterprise databases.
• A centralized database is located at a single site.
• A distributed database is distributed across several different sites.
• An operational database supports a company's day-to-day operations, and is known as a transactional or production database.
• A data warehouse stores data used for tactical or strategic decisions.
• Unstructured data exists in its original state.
• Structured data results from formatting, based on the type of processing to be performed.
• Semistructured data has been processed to some extent.
• Extensible Markup Language (XML) represents data elements in textual format, and an XML database supports semistructured XML data.

Why Database Design is Important

• Database design focuses on designing a database structure for end user data, where a desginer must identify the database's expected usage.
• A well designed database facilitates data management and generates valuable information.
• A poorly designed database may cause difficult-to-trace errors.

Evolution of File System Data Processing

• Understanding file systems allows for easier database design and helps avoid issues with DBMS systems, knowledge of file systems is useful for converting file systems to a database system.
• File systems are typically composed of collections of file folders, each tagged and kept in cabinets, and organized by its expected use.
• The contents of a file folder are logically related.
• Manual file systems served as data repositories for small data collections, with a cumbersome process for large collections.
• With computerized file systems a Data Processing (DP) specialist converted computer file structure from manual system, and wrote software that managed the data, and designed the application programs.
• Initially, computer file systems resembled manual systems.
• As number of files increased, file systems evolved, where each file used its own application program to store, retrieve, and modify data.
• Each file was owned by the individual or department that commissioned its creation.

File System Redux: Modern End-User Productivity Tools

• The use of personal productivity tools can introduce the same problems as the old file systems.
• Microsoft Excel is widely used in the business sector.
• Users adept with spreadsheets use them to complete tasks, which databases are more suitable for.

Problems with File System Data Processing

• File systems were an improvement over a manual system, and were used for more than 2 decades.
• Even a simple file system retrieval task required extensive programming.
• Ad hoc queries were impossible, and changing existing structures was difficult.
• Security features are difficult to program and are often omitted in file system environments.
• File systems have limitations such as requiring excessive programming and being unable to perform ad hoc queries.
• System administration is also difficult, making changes to existing structures is complex, and there is a greater chance of inadequate security features.

Structural and Data Dependence

• Structural dependence accesses a file that is dependent on its own structure.
• Structural independence means you can change a file structure without affecting data access
• Data dependence causes data access to chnage when storage characteristics change.
• Data independence means data storage characteristics do not affect data access.
• Practical significance of data dependence is difference between logical and physical format
• Logical data format reflects how humans view the data.
• Physical data format describes how a computer is meant to work with the data.
• Each program must contain lines that specify the opening of a specific file type, the record specification, and the field definitions.

Data Redundancy

• File system structure makes it difficult to combine data from multiple sources.
• Orgnaizational structures may promote storage of same data in different locations, creating "islands of information".
• Data redundancy involves the same unnecessary data stored in different places.
• Data inconsistency involves different & conflicting versions of same data existing at different places.
• Data anomalies include abnormalities when changes in all redundant data are not made correctly, such as update/insertion/deletion anomalies.

Lack of Design and Data-Modeling Skills

• Most user lack the skills to properly design databases using productivity tools.
• Data-modeling skills are vital in the design process for a database.
• Good data modelling can facilitate communication between the desginer, user, and the developer.

Database Systems

• A database consists of logically related data, stored in a single logical data repository
• Distributed among multiple storage facilities
• The DBMS aims to eliminates most of the problems that are found in file systems.
• Current generation of databses store data structures, relationships between structures, and access paths, as well as defines, stores, and manages all access paths and components.

The Database System Environment

• Database systems define and regulate the collection, storage, management, and use of data.
• There are 5 parts of a database system: hardware, software, people, procedures, and data.
• Hardware refers to the system's physical devices.
• Software refers to the three types of software that are required; Operating system software, DBMS software, and application programs.
• People refers to all users of the database system; system and database administrators, database designers, system analysts and programmers, and end users.
• Procedures refers to the instructions and rules that govern the use of the database system.
• Data is the collection of facts stored in the database.
• Database systems are created and managed at different levels of complexity, where database solutions ideally would be cost-effective, and database technology that is already in place may affect the selection of future systems.

DBMS Functions

• Most of the DBMS functions are transparent to end users, and can only be achieved through the DBMS.
• The DBMS supports data dictionary management by storing definitions of data elements and relationships, in a data dictionary.
• The DBMS will locate data component structures/relationships and record the changes automatically in the dictionary. This also provides data abstraction and removes structural dependency.
• This includes data storage management (creating & managing complex structures), storing data entry forms/screen definitions/report definitions, activities that make the DB perform effectively, and stores the database in multiple physical data files.
• Data transformation and presentation features transforms the entered data to conform to to required data structures, & physically retrieved data to conform to the users expectations.
• Security management includes creating security systems & rules so that users have appropriate level of access.
• Multi-user access control features use sophisticated alogrithms to ensure concurrent access has no affect on data integrity.
• Backup and Recovery Managment features ensure data safety & and integrity through providing backup, data recovery, and recovering the database after a failure.
• Data integrity management promotes and enforces integrity in data by minimizing redundancy & maximizing consistency, using data relationships stored in the dictionary.
• Database access languages and API uses DBMS to provide access through a query language; Structured Query Language (SQL) is the de facto language.
• Database communication interfaces accept end-user requests through network environments; DBMS generates answers to queries by filling screen forms via browser, automatically publishes predefined reports on a website, and conencts to third-party systems for email.

Managing the Database System: A Shift in Focus

• Database system provides a framework in which procedures and standards are enforced, shifting control from programming to managing resources.
• Databases enables more sophisticated data usage, where data structures created within the database and relationships determine how effective it is.
• Disadvantages of using a database system include; increased costs, management complexity, difficulty in maintaining currnecy, vendory dependency, & frequent upgrade/replacement cycles.

Summary

• Data is raw facts, where information is the result of processing that data to reveal its meaning.
• Accurate and timely data are important for good decision making.
• Data can be stored in databases, where it's contents are managed by a DBMS.
• With databases, users deal with metadata, which is data about data, and is well-defined by database design.
• Databases design facilitated data management while poorly created ones lead to poor results.
• Databases have evolved from computerized file and manual systems, and store data in independent files.
• Limitations of file systems may include; complex management, difficult administration, inadequate security, redundant data, and structural/data dependency problems.
• As such, database management systems were developed to address the weaknesses.
• DBMS presents information in a way that is easy for the user to understand.
• Data integrity is made more secure in such a system.