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CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
JULY15
ASSESSMENT_CODE MIT202_JULY15
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
13029
QUESTION_TEXT
Explain DDL and DML in DBMS.
SCHEME OF
EVALUATION
Two main types of facilities are supported by the DBMS: the data
definition facility or Data Definition Language(DDL), the Data
Manipulation facility or the Data Manipulation Language (DML)
Data Definition Language:
a.This can be used to define the conceptual schema and also give some
details about how to implement this schema in the physical devices used
to store data. ( 1 mark)
b.This definition includes all the entity sets and their associated
attributes, as well as the relationships among the entity sets. ( 1 mark)
c.The definition also includes any constraints that have to be maintained,
including the constraints on the value that can be assigned to a given
attribute, and the constraints on the values assigned to different
attributes in the same or different records. ( 1 mark)
d.These definitions, which can be described as metadata about the data
in the data base, are expressed in the DDL of the DBMS and maintained
in a compiled form. ( 1 mark)
e.The internal schema is specified in a somewhat similar data definition
language called data storage definition language. ( 1 mark)
Data Manipulation Language
a.Is a language that enables users to access or manipulate as organized
by the appropriate data model.
b.Data manipulation involves retrieval of data from the database,
insertion of new data into he database, and deletion or modification of
existing data.
c.The first of these data manipulation operations is called a Query. A
Query is a statement in the DML that requests the retrieval of data from
the database. The subset of the DML used to pose a query is known as a
query language.
d.The DML provides commands to select and retrieve data from the
database. Commands are also provided to insert, update and delete
records.
e.There are basically two types of DML:
i.Procedural: requires a user to specify what data is needed and how to
get it.
ii.Nonprocedural: requires a user to specify what data is needed without
specifying how to get it. ( 1 X 5=5 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
72999
QUESTION_TEXT
Give an account of various Keys used in DBMS.
SCHEME OF
EVALUATION
Keys: The key uniquely differentiates one entity instance from all others in
the entity. A key is an identifier.
Primary Key: Identifier used to uniquely identify one particular instance of an
entity.
A primary key
• Can be one or more attributes
• Must be unique within the domain
• Its value should not change over time
• Must always have a value
• Is created when no obvious attribute exists. Each instance has a value.
• Candidate Key: When multiple possible identifiers exist, each of them is
a candidate key.
• Concatenated Key: Key made up of parts which, when combined,
become a unique identifier. Multiple attribute keys are concatenated keys.
• Foreign Keys: Foreign keys reference a related table through the
primary key of that related table.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73001
QUESTION_TEXT
Explain different types of Databases.
SCHEME OF
EVALUATION
• Design databases: Engineering design databases are useful in computeraided design / manufacturing / software engineering (CAD / CAM / CASE)
systems. In such systems, complex objects can be recursively partitioned into
smaller objects. Furthermore, an object can have different representations at
different levels of abstraction.
• Multimedia databases: In modern office information or other multimedia
systems, data includes not only text and numbers but also images, graphics
and digital audio and video. Such multimedia data is typically stored as
sequences of bytes with variable lengths, and segments of data are linked
together for easy reference.
• Knowledge bases: Artificial intelligence and expert systems represent
information as facts and rules that can be collectively viewed as a knowledge
base. In typical AI applications, knowledge representation requires data
structures with rich semantics that go beyond the simple structure of the
relational model. Artificial decomposition and mapping would be necessary if a
relational DBMS were used.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
118841
QUESTION_TEXT
SCHEME OF
EVALUATION
Explain different categories of SQL commands.
•
SQL commands can be roughly divided into 3 major
categories with regard to their functionality.
a.
Data Definition Statements: (04 marks)
•
Used to create and maintain the database structure.
•
2 major DDL statements CREATE and DROP.
•
CREATE DATABASE to create a database.
•
DROP DATABASE to remove a database.
•
CREATE TABLE create table.
•
DROP TABLE to drop a table.
•
CREATE INDEX to create an index on a column.
•
DROP INDEX to drop index.
•
CREATE VIEW to create view.
•
DROP VIEW drop a view.
b.
Data Manipulation Statements: (02 marks)
To manipulate data in tables directly or through views 4
standard DML statements: SELECT DELETE INSERT UPDATE
c.
Data Control: (04 marks)
3 issues
a.
Recovery and concurrency:
•
Manner in which multiple users operate upon the data base
•
Reflect updates of a transaction by using the COMMIT.
•
Cancel all updates using ROLLBACK.
b.
Security: 2 aspects
•
GRANT-this shall grant one or more access rights to perform
the data manipulative operations on the relations.
•
VIEW mechanism it can be created which hides the sensitive
information and defines only that part of a relation which should be
visible.
•
A user can then be allowed to access this view
•
Ex: CREATE VIEW LOCAL AS
SELECT * FROM SUPPLIER
WHERE SUPPLIER.CITY=’Delhi’
c.
Integrity constraints: ex: one can specify that an attribute of
a relation will not take on null values.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
118844
Explain the different types of Normal forms with examples.
QUESTION_TEXT
SCHEME OF EVALUATION i.
First Normal form – 2 Marks
ii.
iii.
iv.
v.
Second normal form – 2 Marks
Third normal form – 2 Marks
Fourth Normal Form – 2 Marks
Boyce Cod Normal Form – 2 Marks
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
118847
QUESTION_TEXT
List and explain the important responsibilities of Database manager.
SCHEME OF
EVALUATION
The important responsibilities of Database Manager:
a.
Interaction with file manager: The raw data is stored on the disk
using the file system which is usually provided by a conventional
operating system. Database manager is responsible for the actual storing,
retrieving and updating of data in the database.
b.
Integrity enforcement: The data values stored in the database
must satisfy certain types of consistency constraints. Example: the
balance of a bank account may never fall below a prescribed amount. In
such cases database manager can check the system.
c.
Security enforcement: Not every user of the database needs to
have access to the entire content of the database. It is the job of the
database manager to enforce these security requirements.
d.
Backup and recovery: A computer system like any other system
may fail; hence the information concerning the database is lost. It is the
responsibility of the Database manger to detect such failures, and restore
the database.
e.
Concurrency Control: When several users update the database
concurrently, the consistency of data may no longer be preserved. It is
necessary for the system to control the interaction among concurrent
users and achieving such a control is one of the responsibilities of
database manager. (2 X 5= 10 marks)