It is a particular property, which describes the entity.
What is a Relation Schema and a Relation ?
A relation Schema denoted by R(A1, A2, .., An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).
What is degree of a Relation ?
It is the number of attribute of its relation schema.
What is Relationship ?
It is an association among two or more entities.
What is Relationship set ?
The collection (or set) of similar relationships.
What is Relationship type ?
Relationship type defines a set of associations or a relationship set among a given set of entity types.
What is degree of Relationship type ?
It is the number of entity type participating.
What is DDL (Data Definition Language) ?
A data base schema is specifies by a set of definitions expressed by a special language called DDL.
What is VDL (View Definition Language) ?
It specifies user views and their mappings to the conceptual schema.
What is SDL (Storage Definition Language) ?
This language is to specify the internal schema. This language may specify the mapping between two schemas.
What is Data Storage - Definition Language ?
The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.
What is DML (Data Manipulation Language) ?
This language that enable user to access or manipulate data as organised by appropriate data model.
Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.