41) Define The Types Of Data Integrity Rules?
Answer: Data Integrity falls under the following three categories:
a) Entity Integrity: Entity integrity ensures that each row can be uniquely identified by an attribute
called the Primary key. The Primary key cannot have a NULL value.
b) Domain Integrity:Domain integrity refers to the range of valid entries for a given column. It ensures that there are only valid entries in the column.
c) Referential Integrity: Referential integrity ensures that for every value of a Foreign key, there is a
matching value of the Primary key. It states that "Foreign Key can be either a NULL value or should be Primary Key value of other relation".
42) What Is A Table? What Is A Tuple? What Is A Relation?
Answer: Table is a representation of a relation having records as rows and attributes as columns.
Tuple is nothing but a row in a table.
A relation consists of a homogeneous set of tuples. Informally a relation is a table.
Relations can be represented as two-dimensional data tables with rows and columns. The rows of a relation are called tuples. The columns of a relation are called attributes.
The attributes draw values from a domain (a legal pool of values). The number of tuples in a relation is called its cardinality while the number of attributes in a relation is called its degree.
A relation also consists of a schema and an instance. Schema defines the structure of a relation which consists of a fixed set of attribute domain pairs. An instance of a relation is a time-varying set of tuples where each tuple consists of attribute-value pairs.
43) What Are Extension & Intension?
Answer: Extension is the number of tuples (rows) present in a table at any instance. This is time dependent where as Intension is a constant value that gives the name, structure of table and the constraints laid on it.
A database is divided into schema and data. The schema describes the intentions (types) and the data describes the extension (data).
44) What Is A View? How It Is Related To Data Independence?
Answer: A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence.
45) What Is A View? Discuss The Difference Between A View & A Base Relation?
Answer: View is the dynamic result of one or more relational operations operating on the base relations to produce another relation.
Base relation exists as a set of data in the database. A view does not contain any data, rather a view is defined as a query on one or more base relations and a query on the view is translated into a query on the associated base relations.
ALSO CHECK THE BELOW FAQ's:
46) What Is A Key? What Are Different Types Of Keys In A Database?
47) What Is A Primary Key & Secondary Key?
48) What Is A Candidate Key & Alternate Key?
49) What Is A Super Key & Composite Key?
50) What Is Foreign Key?
51) What Is Normalization. Explain It In Detail?
52) What Is The Need For Normalization In DBMS?
53) What Are The Goals Of Normalization In DBMS?
54) State The Benefits Of Normalization In DBMS?
55) What Is Functional Dependency?
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