INTRODUCTION TO DATABASE

A database is a set of data that has a regular structure and that is organized in such a way that a computer can easily find the desired information. Data is a collection of distinct pieces of information, particularly information that has been formatted (i.e ., organized) in some specific way for use in analysis or making decisions. A database is a collection of information that is organized so that it can easily be accessed, managed, and updated. In one view, databases can be classified according to types of content: bibliographic, full-text, numeric, and images.

A database can generally be looked at as being a collection of records, each of which contains one or more fields(i.e.,pieces of data) about some entity (i.e ., object), such as a person, organization, city, product, work of art, recipe, chemical, or sequence of DNA. For example, the fields for a database that is about people who work for a specific company might include the name, employee identification number, address, telephone number, date employment started, position and salary for each worker.

A database is a large collection of data entered a computer system and stored for future use. The computerized information in the database is organized so that the parts that have something in common can be retrieved easily. The term database was originally written as data base, and it may have been first used in 1963 at a symposium sponsored by the System Development Corporation of Santa Monica, California. The use of the term database (single word) became popular in some European countries in the early 1970s, and it subsequently spread to the U.S.

 

DATABASE MANAGEMENT SYSTEM (DBMS)

A database management system is the system in which related data is stored in an efficient or compact manner. “Efficient” means that the data which is stored in the DBMS can be accessed quickly and “compact” means that the data takes up very little space in the computer’s memory. The phrase “related data” means that the data stored pertains to a particular topic.

A database management system (DBMS) is the software that allows a computer to perform database functions of storing, retrieving, adding, deleting and modifying data. Relational database management systems (RDBMS) implement the relational model of tables and relationships.

Examples are Microsoft Access, MySQL, Microsoft SQL Server, Oracle, Dbase 111, Dbase IV, Foxbase, Rbase and FileMaker Pro.

Specialized databases have existed for scientific, imaging, document storage and like uses. The DBMS of today roll together frequently needed services and features of attribute management. By externalizing such functionality to the DBMS, applications effectively share code with each other and are relieved of much internal complexity.

 

Features of Database Management Systems

1. Query ability: Querying is the process of requesting attribute information from various perspectives and combination of factors. Example: “How many 4 -door cars in Nigeria are green?” A database query language and report writer allow users to interactively interrogate the database, analyze its data and update it according to the users privileges on data.
2. Backup and replication: Copies of attributes need to be made regularly in case primary disks or other equipment fails. A periodic copy of attributes may also be created for a distant organization that cannot readily access the original. DBMS usually provide utilities to facilitate the process of extracting and disseminating attribute sets. When data is replicated between database servers, so that the information remains consistent throughout the database system and users cannot tell or even know which server in the DBMS they are using, the system is said to exhibit replication transparency.
3. Rule enforcement: Often one wants to apply rules to attributes so that the attributes are clean and reliable. For example, we may have a rule that says each car can have only one engine associated with it (identified by Engine Number). If somebody tries to associate a second engine with a given car, we want the DBMS to deny such a request and display an error message.
4. Security: For security reasons, it is desirable to limit who can see or change specific attributes or groups of attributes. This may be managed directly on an individual basis, or by the assignment of individuals and privileges to groups, or (in the most elaborate models) through the assignment of individuals and groups to roles which are then granted entitlements.
5. Computation: Common computations requested on attributes are counting, summing, averaging, sorting, grouping, cross-referencing, and so on. Rather than have each computer application implement these from scratch, they can rely on the DBMS to supply such calculations.
6. Change and access logging: This describes who accessed which attributes, what was changed, and when it was changed. Logging services allow this by keeping a record of access occurrences and changes.
7. Automated optimization: For frequently occurring usage patterns or requests, some DBMS can adjust themselves to improve the speed of those interactions. In some cases the DBMS will merely provide tools to monitor performance, allowing a human expert to make the necessary adjustments after reviewing the statistics collected.

 

COMPONENTS OF DBMS

1. DBMS engine: It accepts logical requests from various other DBMS subsystems, converts them into physical equivalents, and actually accesses the database and data dictionary as they exist on a storage device.
2. Data definition subsystem: It helps the user to create and maintain the data dictionary and define the structure of the file in a database.
3. Data manipulation subsystem: It helps the user to add, change, and delete information in a database and query it for valuable information. Software tools within the data manipulation subsystem are most often the primary interface between user and the information contained in a database. It allows the user to specify its logical information requirements.
4. Application generation subsystem: It contains facilities to help users develop transaction-intensive applications. It usually requires that the user perform a detailed series of tasks to process a transaction. It facilitates easy-to-use data entry screens, programming languages, and interfaces.
5. Data administration subsystem: It helps users manage the overall database environment by providing facilities for backup and recovery, security management, query optimization, concurrency control, and change management.

 

ADVANTAGES OF DBMS

1. Improved availability: One of the principle advantages of a DBMS is that the same information can be made available to different users.
2. Minimized redundancy: The data in a DBMS is more concise because, as a general rule, the information in it appears just once. This reduces data redundancy, or in other words, the need to repeat the same data over and over again. Minimizing redundancy can therefore significantly reduce the cost of storing information on hard drives and other storage devices. In contrast, data fields are commonly repeated in multiple files when a file management system is used.
3. Accuracy: Accurate, consistent, and up-to-date data is a sign of data integrity. DBMSs foster data integrity because updates and changes to the data only have to be made in one place. The chances of making a mistake are higher if you are required to change the same data in several different places than if you only have to make the change in one place.
4. Program and file consistency: Using a database management system, file formats and system programs are standardized. This makes the data files easier to maintain because the same rules and guidelines apply across all types of data. The level of consistency across files and programs also makes it easier to manage data when multiple programmers are involved.
5. User-friendly: Data is easier to access and manipulate with a DBMS than without it. In most cases, DBMSs also reduce the reliance of individual users on computer specialists to meet their data needs.
6. Improved security: As stated earlier, DBMSs allow multiple users to access the same data resources. This capability is generally viewed as a benefit, but there are potential risks for the organization. Some sources of information should be protected or secured and only viewed by select individuals. Through the use of passwords, database management systems can be used to restrict data access to only those who should see it.

 

DISADVANTAGES OF DBMS

There are basically two major downsides to using DBMSs. One of these is cost, and the other the threat to data security.

1. Cost: Implementing a DBMS system can be expensive and time-consuming, especially in large organizations. Training requirements alone can be quite costly.
2. Security: Even with safeguards in place, it may be possible for some unauthorized users to access the database. In general, database access is an all or nothing proposition. Once an unauthorized user gets into the database,they have access to all the files, not just a few. Depending on the nature of the data involved, these breaches in security can also pose a threat to individual privacy. Steps should also be taken to regularly make backup copies of the database files and store them because of the possibility of fires and earthquakes that might destroy the system.

 

BENEFITS OF DBMS

1. Improved strategic use of corporate data.
2. Reduced complexity of the organization’s information systems environment.
3. Reduced data redundancy and inconsistency.
4. Enhanced data integrity.
5. Application-data independence.
6. Improved security.
7. Reduced application development and maintenance costs.
8. Improved flexibility of information systems.
9. Increased access and availability of data and information.
10. Logical & Physical data independence.