Introduction To Database Questions and Answers

Q: The way a particular application views the data from the database that the application uses is a

Correct answer: Sub schema.A subschema (external schema) is one application’s view of the database: the subset of tables and columns it needs, possibly renamed or restructured. Several subschemas can sit over one logical schema, which is how different applications share the same data while each seeing only its own part.

Q: Which of the operations constitute a basic set of operations for manipulating relational data?

Correct answer: Relational algebraRelational algebra is the procedural set of basic operations - selection, projection, union, set difference, Cartesian product, and the joins and intersection derived from them. Relational calculus is the non-procedural counterpart: it describes what is wanted rather than how to compute it, and the two have equivalent expressive power.

Q: Hierarchical model is also called

Correct answer: Tree structureThe hierarchical model organises records into a tree: every record type except the root has exactly one parent, and access is by navigating down from the root. That single-parent rule is its limitation - a many-to-many relationship cannot be represented without duplicating data - and it is what the network model, a “plex” or graph structure, was devised to relax.

Q: Relational Algebra is

Correct answer: Procedural query LanguageRelational algebra is procedural: an expression specifies a sequence of operations - select, then project, then join - and so says how the result is to be obtained. Relational calculus and SQL are declarative by contrast.

Q: Key to represent relationship between tables is called

Correct answer: foreign keyA foreign key is a column whose values must appear as a primary key in another table, and that requirement is what represents the relationship between the two. A primary key identifies rows within one table only.

Q: DBMS should provide following feature(s) ______.

Correct answer: All of theseA DBMS must do all three: protect data against a system crash, through logging and recovery; keep the stored information safe, through backup and integrity constraints; and restrict access to authorised users. These are among the central reasons for using a DBMS instead of ordinary files.

Q: The property / properties of a database is / are :

Correct answer: All of the aboveAll three are defining properties. A database is an integrated collection of logically related records; it consolidates what used to be separate files into a common pool; and the data in it is independent of the programs that use it, so the storage can change without rewriting the applications.

Q: What does DDL stand for in SQL ?

Correct answer: Data Definition LanguageDDL comprises the statements that define and alter database structure, such as CREATE, ALTER and DROP. DML, the Data Manipulation Language, covers the statements that work on the rows themselves.

Q: DBMS stands for __________.

Correct answer: Database Management SystemDBMS is Database Management System: the software that stores, retrieves, updates and administers the data, and enforces the rules that keep it consistent.

Q: Prior to 1970, all data was stored in separate files, which were mostly stored on reels of magnetic tape.

Correct answer: TrueBefore the database era, data was held in separate files, each written for one application, and largely on magnetic tape - which allows only sequential access. The consequences were duplicated data, inconsistency between files, and applications that broke whenever a file’s layout changed. Those problems are what databases were invented to solve.

91.

The way a particular application views the data from the database that the application uses is a

A.Module.
B.Relational model.
C.Schema.
D.Sub schema.

Answer: D

Correct answer: Sub schema.

A subschema (external schema) is one application’s view of the database: the subset of tables and columns it needs, possibly renamed or restructured. Several subschemas can sit over one logical schema, which is how different applications share the same data while each seeing only its own part.

Discuss in Forum

92.

Which of the operations constitute a basic set of operations for manipulating relational data?

A.Predicate calculus
B.Relational calculus
C.Relational algebra
D.None of the above

Answer: C

Correct answer: Relational algebra

Relational algebra is the procedural set of basic operations - selection, projection, union, set difference, Cartesian product, and the joins and intersection derived from them. Relational calculus is the non-procedural counterpart: it describes what is wanted rather than how to compute it, and the two have equivalent expressive power.

Discuss in Forum

93.

Hierarchical model is also called

A.Tree structure
B.Plex Structure
C.Normalize Structure
D.Table Structure

Answer: A

Correct answer: Tree structure

The hierarchical model organises records into a tree: every record type except the root has exactly one parent, and access is by navigating down from the root. That single-parent rule is its limitation - a many-to-many relationship cannot be represented without duplicating data - and it is what the network model, a “plex” or graph structure, was devised to relax.

Discuss in Forum

94.

Relational Algebra is

A.Data Definition Language
B.Meta Language
C.Procedural query Language
D.None of the above

Answer: C

Correct answer: Procedural query Language

Relational algebra is procedural: an expression specifies a sequence of operations - select, then project, then join - and so says how the result is to be obtained. Relational calculus and SQL are declarative by contrast.

Discuss in Forum

95.

Key to represent relationship between tables is called

A.Primary key
B.Secondary Key
C.Foreign Key
D.None of these

Answer: C

Correct answer: foreign key

A foreign key is a column whose values must appear as a primary key in another table, and that requirement is what represents the relationship between the two. A primary key identifies rows within one table only.

Discuss in Forum

96.

DBMS should provide following feature(s) ______.

A.Protect data from system crash
B.All of these
C.Safety of the information stored
D.Authorized access

Answer: B

Correct answer: All of these

A DBMS must do all three: protect data against a system crash, through logging and recovery; keep the stored information safe, through backup and integrity constraints; and restrict access to authorised users. These are among the central reasons for using a DBMS instead of ordinary files.

Discuss in Forum

97.

The property / properties of a database is / are :

A.It is an integrated collection of logically related records.
B.It consolidates separate files into a common pool of data records.
C.Data stored in a database is independent of the application programs using it
D.All of the above

Answer: D

Correct answer: All of the above

All three are defining properties. A database is an integrated collection of logically related records; it consolidates what used to be separate files into a common pool; and the data in it is independent of the programs that use it, so the storage can change without rewriting the applications.

Discuss in Forum

98.

What does DDL stand for in SQL ?

A.Data Definition Language
B.Data Description Logic
C.Dynamic Data Language
D.Database Design Layer

Answer: A

Correct answer: Data Definition Language

DDL comprises the statements that define and alter database structure, such as CREATE, ALTER and DROP. DML, the Data Manipulation Language, covers the statements that work on the rows themselves.

Discuss in Forum

99.

DBMS stands for __________.

A.None of these
B.Database Administrator System
C.Database Basic Management System
D.Database Management System

Answer: D

Correct answer: Database Management System

DBMS is Database Management System: the software that stores, retrieves, updates and administers the data, and enforces the rules that keep it consistent.

Discuss in Forum

100.

Prior to 1970, all data was stored in separate files, which were mostly stored on reels of magnetic tape.

A.True
B.False
C.None of the Above.
D.All of the Above.

Answer: A

Correct answer: True

Before the database era, data was held in separate files, each written for one application, and largely on magnetic tape - which allows only sequential access. The consequences were duplicated data, inconsistency between files, and applications that broke whenever a file’s layout changed. Those problems are what databases were invented to solve.

Discuss in Forum

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