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Structured Query Language Made Simple
Fukula Hastings Nyekanyeka

Relational Databases Overview

Database - A database is a structured collection of data. Data refers to the characteristics of people, things, and events. Normally a database refers to a collection of tables.

Table - The group of all fields for a specific Entity.

Entity - Person, place, object, event, or idea.

Field (attribute) - single characteristic of an entity.

Field Value - Contents of a field.

Common Field - a field that appears in 2 tables.

Primary key - A field or combination of fields that uniquely identify each record in a table. Every table in a database has a field or a combination of fields that uniquely identifies each record in the table. This unique identifier is called the primary key, or simply the key. The primary key provides the means to distinguish one record from all the others in a table. It allows the user and the database system to identify, locate, and refer to one particular record in the table.

Foreign Key - A primary key of one table that is added to a second table to form a relationship. The foreign key is in the second table.

Relational Database - a collection of tables whose data is related. Sometimes all the information of interest to an operation can be stored in one table. For example, a college registrar's office would need only one table to keep all basic student information with the fields first name, last name, date of birth, address and year of entry. However, the registrar's office needs more tables to all the data for the students; from courses to majors to departments and more. For example, there is a table for courses codes and their descriptions, a table for department codes and names. A relational database makes it very easy to link the data in multiple tables: matching an a student to the course in which they are enrolled is one example. This is done through defined relationship between the tables.

Database Management System (DBMS) - A database management system, or DBMS, gives the user access to their data and helps them transform the data into information. They allow users to create, update, and extract information. The advantages of using a DBMS are speed, accuracy, and accessibility. Some DBMS have many utilities or features aimed at ensuring data integrity and security. Examples of database management systems include Oracle, dBase, Paradox, Informix and Sybase.

Relational Database Management System (RDBMS) - A relational database management system, or RDBMS, gives the user access to data in related tables and helps them transform the data into information. Oracle is a relational database management system, or RDBMS since it stores data in two or more tables and enables you to define relationships between the tables based on one or more fields common to both tables.