DBMS Interviews and Answers Part-3
21:What is an attribute?
ANSWER:
It is a particular property, which describes the entity.
It is a particular property, which describes the entity.
22:What is a Relation Schema and a Relation?
ANSWER:
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).
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).
23:What is degree of a Relation?
ANSWER:
It is the number of attribute of its relation schema.
It is the number of attribute of its relation schema.
24:What is Relationship?
ANSWER:
It is an association among two or more entities.
It is an association among two or more entities.
25:What is Relationship set?
ANSWER:
The collection (or set) of similar relationships.
The collection (or set) of similar relationships.
26:What is Relationship type?
ANSWER:
Relationship type defines a set of associations or a relationship set among a given set of entity types.
Relationship type defines a set of associations or a relationship set among a given set of entity types.
27:What is degree of Relationship type?
ANSWER:
It is the number of entity type participating.
It is the number of entity type participating.
28:What is Data Storage - Definition Language?
ANSWER:
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.
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.
29:What is DML (Data Manipulation Language)?
ANSWER:
This language that enable user to access or manipulate data as organised by appropriate data model.
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.
30:What is VDL (View Definition Language)?
ANSWER:
It specifies user views and their mappings to the conceptual schema.
It specifies user views and their mappings to the conceptual schema.