A relation can have multiple candidate keys Tuple : A row in a relation is called a tupleĪttribute : A column in a relation is called an attributeĭomain : Domain of an attribute refers to the set of all the possible values for that attribute.ĭegree : Number of attributes in a relation is the degree of that relationĬardinality : Number of tuples in a relation is the cardinality of that relation.Ĭandidate Key: A set of one or more minimal attributes used to uniquely identify a tuple in the relation and which can act as Primary Key. in any two rows value in at least one column must be different. No duplicity: No two rows of relation will be identical i.e. a value that can not be further subdivided. These tables termed as relation.Ītomicity : At every row-column intersection (Cell) there must be an atomic value i.e.
Physical level without affecting the scheme followed at the conceptual level. Physical Data Independence: It refers to the ability to modify the scheme followed at the It also describes the relationships existing among data.Įxternal Level (View Level) : It is closest to the users and is concerned with the way in which the data are viewed by individual usersĭata Independence: The ability to modify a scheme definition in one level without affecting a scheme definition in the next higher level. Internal Level ( Physical Level) : It describes how the data are actually stored on the storage media.Ĭonceptual Level : It describes what data are actually stored in the database. MySQL, INGRES, POSTGRES, ORACLE, DB2, Microsoft Access. Centralized databases can ensure data security Examples of Common Database Management Systems:.Control data inconsistency to a large extent.Reduce data redundancy (duplication of data).Systems comprising of Databases and Database Management Systems are simply referred as database systems. Since table is a collection of relationships it is generally referred to using the mathematical term Relation. A row in a table represents a relationship among a set of values. In a relational data model, the data is organized into tables (i.e. Relational DataBase Management System (RDBMS):Ī Database Management System that conforms at-least half of the 12 rules defined by Dr. They also provide various safety and security mechanisms that ensures that in any case stored data will be safe and accessible. In short a DBMS provides the means to store the data in the database, to edit or delete the data stored, to search and analyze the data in the database.
DataBase Management System (DBMS)Ĭomprehensive software that provides the essential services to create, manage and maintain the databases. Database:Ī well-organized collection of interrelated data that ensures safety, security and integrity of data is called database. Data Item:Įach piece of information about an entity, such as name of a person or address, age or name of a product or the price is a Data Item. Chapter 8 : Database Management System Data:īasic/raw facts about something which is not organized, for example details of some students which is not organized.