141405-DATABASE MANAGEMENT SYSTEM
TWO MARKS
UNIT: 1
INTRODUCTION:
1. Who is a DBA? What are the
responsibilities of a DBA? April/May-2011
A database administrator (short form
DBA) is a person responsible for the design, implementation, maintenance and repair
of an organization's database. They are also known by the titles Database
Coordinator or Database Programmer, and is closely related to the Database
Analyst, Database Modeller, Programmer Analyst, and Systems Manager. The role
includes the development and design of database strategies, monitoring and
improving database performance and capacity, and planning for future expansion
requirements. They may also plan, co-ordinate and implement security measures
to safeguard the database
2. What is a data model? List the
types of data model used. April/May-2011
A database model is the theoretical
foundation of a database and fundamentally determines in which manner data can be
stored, organized, and manipulated in a database system. It thereby defines the
infrastructure offered by a particular database system. The most popular
example of a database model is the relational model. types of data model used
§Hierarchical model
§Network model
§Relational model
§Entity-relationship
§Object-relational model
§Object model
3. Define database management
system?
Database management system (DBMS) is
a collection of interrelated data and a set of programs to access those data.
4. What is data base management
system?
ØA database management system (DBMS) is a software package with
computer programs that control the creation, maintenance, and the use of a
database.
ØIt allows organizations to conveniently develop databases
for various applications by database administrators (DBAs) and other
specialists.
ØA database is an integrated collection of data records,
files, and other database objects.
ØA DBMS allows different user application programs to
concurrently access the same database. DBMSs may use a variety of database
models, such as the relational model or object model, to conveniently describe
and support
applications.
ØIt typically supports query languages, which are in fact
high-level programming languages, dedicated database languages that
considerably simplify writing database application programs.
ØDatabase languages also simplify the database organization
as well as retrieving and presenting information from it.
ØA DBMS provides facilities for controlling data access,
enforcing data integrity, managing concurrency control, recovering the database
after failures and restoring it from backup files, as well as maintaining
database security.
5. List any eight applications of
DBMS.
a) Banking
b) Airlines
c) Universities
d) Credit card transactions
e) Tele communication
f) Finance
g) Sales
h) Manufacturing
i) Human resources
6. What are the disadvantages of
file processing system?
The disadvantages of file processing
systems are
a) Data redundancy and inconsistency
b)Difficulty in accessing data
c) Data isolation
d) Integrity problems
e) Atomicity problems
f) Concurrent access anomalies
7. What are the advantages of using
a DBMS?
The advantages of using a DBMS are
a) Controlling redundancy
c) Providing multiple user
interfaces
d) Enforcing integrity constraints.
e) Providing back up and recovery
8. Give the levels of data
abstraction?
a) Physical level
b) Logical level
c) View level
9. Define instance and schema?
Instance:
Collection of data stored in the
data base at a particular moment is called an Instance of the database.
Schema:
The overall design of the data base
is called the data base schema.
10. Define the terms
1) Physical schema
2) logical schema.
Physical schema:
The physical schema describes the
database design at the physical level, which is the lowest level of abstraction
describing how the data are actually stored.
Logical schema:
The logical schema describes the
database design at the logical level, which describes what data are stored in
the database and what relationship exists among the data.
11. What is conceptual schema?
The schemas at the view level are
called
subschema‟sthat describe different views of the database.
12. Define data model?
A data model is a collection of
conceptual tools for describing data, data relationships, data semantics and consistency
constraints.
13. What is storage manager?
A storage manager is a program
module that provides the interface between the low level data stored in a
database and the application programs and queries submitted to the system.
14. What are the components of
storage manager?
The storage manager components
include
a) Authorization and integrity
manager
b) Transaction manager
c) File manager
d) Buffer manager
15. What is the purpose of storage
manager?
The storage manager is responsible
for the following
a) Interaction with the file manager
b) Translation of DML commands in to
low level file system commands
c) Storing, retrieving and updating
data in the database
16. List the data structures
implemented by the storage manager
. The storage manager implements the
following data structure
a) Data files
b) Data dictionary
c) Indices
17. What is a data dictionary?
A data dictionary is a data
structure which stores meta data about the structure of the database ie. The
schema of the database.
18. What is an entity relationship
model?
The entity relationship model is a
collection of basic objects called entities and relationship among those
objects.
An entity is a thing or object in
the real world that is distinguishable from other objects.
19. What are attributes? Give
examples.
An entity is represented by a set of
attributes. Attributes are descriptive properties possessed by each member of
an entity set.
Example:
possible attributes of customer
entity are customer name, customer id, Customer Street, customer city.
20. What is relationship? Give
examples
A relationship is an association
among several entities.
Example:
A depositor relationship associates
a customer with each account that he/she has.
21. Define the terms i) Entity set
ii) Relationship set
Entity set:
The set of all entities of the same
type is termed as an entity set.
Relationship set: The set of all
relationships of the same type is termed as a relationship set.
22. Define single valued and
multivalued attributes.
Single valued attributes:
attributes with a single value for a
particular entity are called single valued attributes.
Multivalued attributes: Attributes with
a set of value for a particular entity are called multivalued attributes.
23. What are stored and derived
attributes?
Stored attributes: The attributes stored in a data
base are called stored attributes.
Derived attributes:
The attributes that are derived from
the stored attributes are called derived attributes.
24. What are composite attributes?
Composite attributes can be divided
in to sub parts.
25. Define null values.
In some cases a particular entity
may not have an applicable value for an attribute or if we do not know the
value of an attribute for a particular entity. In these cases null value is
used.
26. Define the terms i) Entity type
ii) Entity set
Entity type:An entity type defines a collection
of entities that have the same attributes.
Entity set:The set of all entities of the same
type is termed as an entity set.
27. What is meant by the degree of
relationship set?
The degree of relationship type is
the number of participating entity types.
28. Define the terms
i) Key attribute
ii) Value set
Key attribute: An entity type
usually has an attribute whose values are
distinct from each individual entity
in the collection. Such an attribute is called a key attribute.
Value set:
Each simple attribute of an entity
type is associated with a value set that specifies the set of values that may
be assigned to that attribute for each individual entity.
29. Define weak and strong entity
sets?
Weak entity set: entity set that do
not have key attribute of their own are called weak entity sets. Strong entity
set: Entity set that has a primary key is termed a strong entity set.
30. What does the cardinality ratio
specify?
Mapping cardinalities or cardinality
ratios express the number of entities to which another entity can be
associated.
Mapping cardinalities must be one of
the following:
• One to one
• One to many
• Many to one
• Many to many
31. Explain the two types of
participation constraint.
• Total:
The participation of an entity set E
in a relationship set R is said to be
Total if every entity in E participates
in at least one relationship in R.
• Partial:
if only some entities in E
participate in relationships in R, the participation of entity set E in relationship
R is said to be partial.
32. Define the terms i) DDL ii) DML
DDL:Data base schema is specified by a
set of definitions expressed by a special language called a data definition language.
DML:A data manipulation language is a
language that enables users to access or manipulate data as organized by the
appropriate data model
UNIT-II
RELATIONAL MODEL:
1. What is embedded SQL? What are
its advantages? April/May-2011
Embedded SQL is a method of
combining the computing power of a
programming language and the database
manipulation capabilities of
SQL. Embedded SQL statements are SQL statements written in line
with the program source code of the host language. The embedded SQL statements
are parsed by an embedded SQL preprocessor
and replaced by host-
language calls to a code library. The output from the
preprocessor is then compiled by the host compiler. This allows programmers to
embed SQL statements in programs written in any number of languages such as:
C/C++, COBOL and Fortran.
2. What is the difference between
tuple relational calculus and domain relational calculus? April/May-2011
The tuple-oriented calculus uses a
tuple variables i.e., variable whose only permitted values are tuples of that
relation. E.g. QUEL.
The domain-oriented calculus has
domain variables i.e., variables that range over the underlying domains instead
of over relation. E.g. ILL, DEDUCE....The tuple-oriented calculus uses a tuple
variables i.e., variable whose only permitted
values are tuples of that relation. E
3. Write short notes on relational
model
The relational model uses a
collection of tables to represent both data and the relationships among those
data. The relational model is an example
of a record based model.
4. Define tuple and attribute
• Attributes:column headers
• Tuple: Row
5.Define the term relation.
Relation is a subset of a Cartesian
product of list domains.
6. Define tuple variable
Tuple variable is a variable whose
domain is the set of all tuples.
7. Define the term Domain.
For each attribute there is a set of
permitted values called the
Domain of that attribute.
8. What is a candidate key?
Minimal super keys are called candidate
keys.
9. What is a primary key?
Primary key is chosen by the database
designer as the principal means of identifying an entity in the entity set.
10. What is a super key?
A super key is a set of one or more
attributes that collectively allows us to identify uniquely an entity in the entity
set.
11. Define- relational algebra.
The relational algebra is a
procedural query language
. It consists of a set of operations
that take one or two relationas input and produce a new relation
as output.
12. What is a SELECT operation?
The Select operation selects tuples
that satisfy a given predicate. We use the lowercase letter ss to denote
selection. ss
13. What is a PROJECT operation?
The project operation is a unary
operation that returns its argument relation with certain attributes left out.
Projection is denoted by pie ( pp pp).
14. Write short notes on tuple
relational calculus.
The tuple relational calculation is
anon procedural query language. It describes the desired information with out giving
a specific procedure for obtaining that Information.
A query or expression can be
expressed in tuple relational calculus as
{t | P (t)} which means the set of
all tuples„t‟
such that predicate P is true for„t‟.
Notations used:
• t[A] the value of tuple „t‟ on attribute, A
• t r tuple „t‟ is in relation „r‟
• there exists
Definition for „there exists‟ ( ):
t r(Q(t)) which means there exists a
tuple „t‟ in
relation „r‟ such
that predicate Q(t) is true.
• for all Definition for „for all‟ ( ): t r(Q(t)) which means Q(t) is true for all tuples „t‟ in relation „r‟.
• Implication
Definition for Implication ( ):
P Q means if P is true then Q must
be true.
15. Write short notes on domain
relational calculus
The domain relational calculus uses
domain variables that take on values from an attribute domain rather than
values for entire tuple.
16. Define query language?
A query is a statement requesting
the retrieval of information. The portion of DML that involves information
retrieval is
called a query language.
17. Write short notes on Schema
diagram.
A database schema along with primary
key and foreign key dependencies can be depicted pictorially by schema diagram.
Each relation appears as a box with
attributes listed inside it and the relation name above it.
18. What is foreign key?
A relation schema r1 derived from an
ER schema may include among its attributes the primary key of another relation
schema r2.this attribute is called a foreign key from r1 referencing r2.
19. What are the parts of SQL
language?
The SQL language h as several parts:
data - definition language
Data manipulation language
View definition
Transaction control
Embedded SQL
Integrity
Authorization
20. What are the categories of SQL
command?
SQL commands are divided in to the
following categories:
1. data - definition language
2. data manipulation language
3. Data Query language
4. data control language
5. data administration statements
6. transaction control statements
21. What are the three classes of
SQL expression?
SQL expression consists of three
clauses:
Select From where
22. Give the general form of SQL
query?
23. What is the use of rename
operation?
Rename operation is used to rename
both r elations and a attributes. It uses the as clause, taking the form: Old-name
As new-name
24. Define tuple variable?
Tuple variables are used for
comparing two tuples in the same relation. The tuple variables are defined in
the from clause by way of the as clause.
25. List the string operations
supported by SQL?
1) Pattern matching Operation
2) Concatenation
3) Extracting character strings
4) Converting between uppercase and
lower case letters.
26. List the set operations of SQL?
1) Union
2) Intersect operation
3) The except operation
27. What is the use of Union and
intersection operation?
Union: The result of this operation
includes all tuples that are either in r1 or in r2 or in both r1 and
r2.Duplicate tuples are automatically eliminated.
Intersection:
The result of this relation includes
all tuples that are in both r1 and r2.
28.What are aggregate functions? And
list the aggregate functions supported by SQL?
Aggregate functions are functions
that take a collection of values as input and return a single value.
Aggregate functions supported by SQL
are
Average: avg
Minimum: min
Maximum: max
Total: sum
Count: count
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