RDBMS Questions
1. What is a Database?
2. What is DBMS?
3 What is a Catalog?
4. What is data ware housing & OLAP?
5. What is real time database technology?
6. What is program-data independence?
7. What is ORDBMS?
8. What is program-operation independence?
9. What is a view?
10. What is OLTP?
11. What is the job of DBA?
12. Who are db designer?
13. What are different types of end users?
14. What are the advantages of using a dbms?
15. What are the disadvantages of using a dbms?
16. What is a data model?
17. What are different categories of data models?
18. What is schema?
19. What are types of schema?
20. What is Data independency?
21. What are different DBMS languages?
22. What are different types of DBMS?
23. What is an entity?
24. What are attributes?
25. What are diff. types of attributes?
26. What is difference between entity set and entity type?
27. What is domain value or value set of an attribute?
28. What is degree of a relationship?
29. What is recursive relationship?
30. What are relationship constraints?
31. What is Cardinality ratio?
32. What is a Participation constraint?
33. What is a weak entity types?
34. What is an ER Diagram?
35. What is an EER?
36. What is specialization?
38. What is generalization?
38. What are constraints on generalization and
specialization?
39. What is a ternary relationship?
40. What is aggregation and association?
41. What is RAID Technology?
42. What is Hashing technique?
43. What are different types of relational constraints?
44. What is difference between a super key, a key, a
candidate key
and a primary key?
45. What is a foreign key?
46. What is a transaction?
47. What are the properties of transaction?
48. What are the basic data base operations?
49. What are the disadvantages of not controlling
concurrency?
50. What are serial, non serial?
51. What are conflict serializable schedules?
52. What is result equivalent?
53. What are conflict equivalent schedules?
54. What is a conflict serializable schedule?
55. What is view equivalence?
56. What is view serializable?
57. What are the various methods of controlling concurrency?
58. What is a lock?
59. What are various types of locking techniques?
60. What is a binary lock?
61. What is shared or exclusive lock?
62. What are different types of two phase lockings(2pl)?
63. What is a deadlock?
64. What are triggers?
1.What is a Database?
Ans: A database is a collection of related data .A database
is a
logically coherent
collection of data with some inherent meaning.
2. What is DBMS?
Ans: Database Management system is a collection of programs
that
enables user to create and maintain a database.
Thus a DBMS is a general purposed s/w system that
facilitates the
process of defining constructing and manipulating a database
for various applications. (Defining a data base involves
specifying
the data types, structures and constraints for the data to
be stored
in the data database.
Constructing a data base is the process of storing data
itself on
some storage medium that is controlled by DBMS. Manipulating
a
database includes such functions as querying the data base
to
retrieve specific data, updating the database to reflect the
changes
in the mini-world.
3. What is a Catalog?
Ans: A catalog is a table that contain the information such
as
structure of each file ,
the type and storage format of each data item and various
constraints on the data .
The information stored in the catalog is called Metadata .
Whenever
a request is
made to access a particular data, the DBMS s/w refers to the
catalog to determine
the structure of the file.
4. What is data ware housing & OLAP?
Ans: Data warehousing and OLAP (online analytical processing
)
systems are the
techniques used in many companies to extract and analyze
useful
information
from very large databases for decision making .
5. What is real time database technology?
Ans: These are all the techniques used in controlling
industrial and
manufacturing
processes.
6. What is program-data independence?
Ans: Unlike in the traditional file sys. the structure of
the data files is
stored in the
DBMS catalog separately from the access programs . This
property
is called
program-data independence.i.e. We needn’t to change the code
of
the DBMS if the
structure of the data is changed .Which is not supported by
traditional file sys .
7. What is ORDBMS?
Ans: Object oriented RDBMS is a relational DBMS in which
every
thing is treated as
objects. User can define operations on data as a part of the
database definition.
8. What is program-operation independence?
Ans: An operation is specified in two parts .
1. Interface (operation name and data types of its
arguments).
2. Implementation (the code part)
The implementation part can be changed without affecting the
interface. This is called
program-operation independence.
9. What is a view?
Ans: A view may be a subset of the database or it may
contain
virtual data that is
derived from the database files but is not explicitly stored
.
10. What is OLTP?
Ans: Online transaction processing is an application that
involve
multiple database accesses
from different parts of the world . OLTP needs a multi-user
DBMS
s/w to ensure that concurrent
transactions operate correctly.
11. What is the job of DBA?
Ans: A database administrator is a person or a group
responsible
for authorizing access to the
database, for coordinating and monitoring its use, and for
acquiring
s/w and h/w resources as needed.
12. Who are db designer?
Ans: Data base designers are responsible for identifying the
data to
be stored in the database and for
choosing appropriate structure to represent and store this
data .
13. What are different types of end users?
Ans:
1. Casual end-users
2. Naive or parametric end users
3. Sophisticated end users
4. Stand alone users.
14. What are the advantages of using a dbms?
Ans:
1. Controlling redundancy.
2. Restricting unauthorized access.
3. Providing persistent storage for program objects and data
structures.
4. Permitting inferencing and actions using rules.
5. Providing multi-user interfaces.
6. Representing complex relationships among data.
7. Enforcing integrity constraints.
8. Providing backups and recovery.
15. What are the disadvantages of using a dbms?
Ans:
1. High initial investments in h/w, s/w, and training.
2. Generality that a DBMS provides for defining and
processing
data.
3. Overhead for providing security, concurrency control,
recovery,
and integrity functions.
16. What is a data model?
Ans: It is a collection of concepts that can be used to
describe the
structure of a database. It provides necessary means to
achieve this
abstraction. By structure of a database we mean the data
types,
relations, and constraints that should hold on the data.
17. What are different categories of data models?
Ans:
1. High-level or conceptual data models.
2. Representational data models.
3. Low-level or physical data models.
High level data models provide the concepts that are close
to the
way many users perceive data.
Representational data models are provide concepts that
provide the
concepts that may be understood by end users but that are
not too
far removed from organization of data in the database.
Physical data models describe the details of how data is
stored in
the computers.
18. What is schema?
Ans: The description of a data base is called the database
schema
, which is specified during database design and is not
expected to
change frequently . A displayed schema is called schema diagram
.We call each object in the schema as schema construct.
19. What are types of schema?
Ans:
1. internal schema.
2. Conceptual schema.
3. External schemas or user views.
20. What is Data independency?
Ans: Data independency is defined as the capacity to change
the
conceptual schema without having to change the schema at the
next higher level. We can define two types of data
independence:
1. Logical data independence.
2. Physical data independence.
LDI is the capacity to change the conceptual schema without
having
to change external schemas or application programs.
PDI is the capacity to change the internal schema without
having to
change conceptual (or external) schemas.
21. What are different DBMS languages?
Ans:
1. DDL (Data definition language)
2. SDL (Storage definition language)
3. VDL (View definition language)
4. DML (Data manipulation language)
22. What are different types of DBMS?
Ans:
1. DBMS
2. RDBMS (Relational)
3. ORDBMS (Object Relational)
4. DDBMS (Distributed)
5. FDBMS (Federated)
6. HDDBMS (Homogeneous)
7. HDBMS (Hierarchical)
8. NDBMS (Networked)
23. What is an entity?
Ans: An entity is a thing in the real world with an
independent
existence.
24. What are attributes?
Ans: These are the particular properties that describe an
entity.
25. What are diff. types of attributes?
Ans:
1. Composite Vs simple attributes.
2. Single valued Vs multi-valued attributes.
3. Stored Vs derived attribute.
4. Null valued attributes.
5. Complex attributes.
26. What is difference between entity set and entity type?
27. What is domain value or value set of an attribute?
Ans: It is the set of values that may be assigned to that
attribute for
each individual entities .
28. What is degree of a relationship?
Ans: The no of entities participating in that relation .
29. What is recursive relationship?
Ans: It is the relationship where both the participating
entities
belong to same entity type .
30. What are relationship constraints?
Ans:
1. Cardinality ratio.
2. Participation constraints.
31. What is Cardinality ratio?
Ans: The cardinality ratio for a binary relationship
specifies the
number of relationship instances that an entity can
participate in.
32. What is a Participation constraint?
Ans: The participation constraint specifies whether the
existence of
an entity depends on its being related to another entity via
the
relationship type. This is of two types:
1. Total participation.
2. Partial participation.
33. What is a weak entity types?
Ans: The entity types that do not have key attributes of
their own
are called weak entity types.
Rests are called strong entity types .The entity that gives
identity to
a weak entity is called owner entity. And the relationship
is called
identifying relationship. A weak entity type always has a
total
participation constraint with respect to its identifying
relationship.
34. What is an ER Diagram?
Ans:
This data model is based on real world that consists of
basic objects
called entities and of relationship among these objects.
Entities are
described in a database by a set of attributes.
35. What is an EER?
Ans:
==
36. What is specialization?
Ans: It is the process of defining a set of subclasses of an
entity
type where each subclass contain all the attributes and
relationships
of the parent entity and may have additional attributes and
relationships which are specific to itself.
37. What is generalization?
Ans: It is the process of finding common attributes and
relations of
a number of entities and defining a common super class for
them.
38. What are constraints on generalization and
specialization?
Ans:
1. disjoint ness constraints.
2. Completeness constraints.
Disjointness constraint specifies that the subclasses of the
specialization must be disjoint .i.e. an entity can be a
member of at
most one of the subclasses of the specialization. The
reverse of it is
overlapping.
Completeness constraint is a participation constraint which
may be
1. Total
2. Partial
Total specialization constraint tells that each entity in
the super
class must be a member of some subclass in the
specialization.
And partial specialization constraint allows an entity not
to belong to
any of the subclasses .Thus we do have the following 4 types
of
constraints on specialization:
1. Disjoint, total
2. Disjoint, partial
3. Overlapping, total
4. Overlapping, partial
39. What is a ternary relationship?
Ans: A relationship with a degree 3 is called a ternary
relationship.
40. What is aggregation and association?
Ans: Aggregation is an abstraction concept for building
composite
objects from their component objects. The abstraction of
association
is used to associate objects from several independent
classes.
41. What is RAID Technology?
Ans: Redundant array of inexpensive (or independent) disks.
The
main goal of raid technology is to even out the widely
different rates
of performance improvement of disks against those in memory
and
microprocessor. Raid technology employs the technique of
data
striping to achieve higher transfer rates.
42. What is Hashing technique?
Ans: This is a primary file organization technique that
provides very
fast access to records on certain search conditions. The
search condition must be an equality condition on a single
field,
called hash field of the file.
1. Internal hashing
2. External hashing
3. Extendible hashing
4. Linear hashing
5. Partitioned hashing
43. What are different types of relational constraints?
Ans:
1. Domain constraints
2. Key constraints
3. Entity integrity constraints
4. Referential integrity constraints
Domain constraints specify that the value of each attribute
must be
an atomic value from the domain of the attributes.
Key constraints tell that no two tuples can have the same
combination of values for all their attributes.
Entity integrity constraint states that no primary key value
can be
null.
Referential integrity constraints states that a tuple in one
relation
that refers to another relation must refer to an existing
tuple in that
relation it is specified between two relations and is used
to maintain
the consistency among tuples of the two relations.
44. What is difference between a super key, a key, a
candidate
key and a primary key?
Ans: A super key specifies a uniqueness constrain that no
two
distinct tuples in a state
can have the same value for the super key. Every relation
has at
least one default super key.
A key is a minimal super key or the subset of the super key
which is
obtained after
removing redundancy. A relation schema may have more than
one
key .In this case
each key is called a candidate key. One of the candidate key
with
minimum number
of attributes is chosen as primary key.
45. What is a foreign key?
Ans: A key of a relation schema is called as a foreign key
if it is the
primary key of
some other relation to which it is related to.
46. What is a transaction?
Ans: A transaction is a logical unit of database processing
that
includes one or more
database access operations.
47. What are the properties of transaction?
Ans:
1. Atomicity
2. Consistency preservation
3. Isolation
4. Durability (permanence)
48. What are the basic data base operations?
Ans:
1. Write_item(x)
2. Read_item(x)
49. What are the disadvantages of not controlling
concurrency?
Ans:
1. Lost update problem
2. Temporary update(Dirty read) problem
3. Incorrect summary problem
50. What are serial, non serial?
Ans: A schedule S is serial if, for every transaction T
participating in
the schedule, all the operations of T is executed
consecutively in the
schedule, otherwise, the schedule is called non-serial
schedule.
51. What are conflict serializable schedules?
Ans: A schedule S of n transactions is serializable if it is
equivalent
to some serial schedule of the same n transactions.
52. What is result equivalent?
Ans: Two schedules are called result equivalent if they
produce the
same final state of the data base.
53. What are conflict equivalent schedules?
Ans: Two schedules are said to be conflict equivalent if the
order of
any two conflicting operations is the same in both
schedules.
54. What is a conflict serializable schedule?
Ans: A schedule is called conflict serializable if it is
conflict
equivalent to some serial schedule.
55. What is view equivalence?
Ans: Two schedules S and S’ are said to be view equivalent
if the
following three conditions hold :
1. Both S and S’ contain same set of transactions with same
operations in them.
2. If any read operation read(x) reads a value written by a
write
operation or the original value of x the same conditions
must hold in
the other schedule for the same read(x) operation.
3. If an operation write1(y) is the last operation to write
the value of
y in schedule S then the same operation must be the last
operation
in schedule S’.
56. What is view serializable?
Ans: A schedule is said to be view serializable if it is
view
equivalent with some serial schedule.
57. What are the various methods of controlling concurrency?
Ans:
1. Locking
2. Time stamp
Locking data item to prevent multiple transactions from
accessing
the item concurrently.
A time stamp is a unique identifier for each transaction,
generated
by the system.
58. What is a lock?
Ans: A lock is a variable associated with a data item that
describes
the status of the item with respect to the possible
operations that
can be applied to it.
59. What are various types of locking techniques?
Ans:
1. a binary lock
2. Shared/Exclusive lock
3. Two phase locking
60. What is a binary lock?
Ans: A binary lock can have two states or values:
1. locked (1)
2. unlocked(0)
If locked it cannot be accessed by any other operations,
else can
be.
61. What is shared or exclusive lock?
Ans: It implements multiple-mode lock. Allowing multiple
accesses
for read operations but exclusive access for write
operation.
62. Explain two phase locking?
Ans: All the locking operations must precede the first
unlock
operation in the transaction .It does have two phases:
1. expanding phase (Locks are issued)
2. Shrinking phase (Locks are released)
63. What are different types of two phase lockings (2pl)?
Ans:
1. Basic
2. Conservative
3. Strict
4. Rigorous
this is the basic technique of 2pl described above.
Conservative 2pl requires a transaction to lock all the
items it
accesses before the transaction begins its execution, by
pre-
declaring it’s read-set and write-set.
Strict 2pl guarantees that a transaction doesn’t release any
of its
exclusive locks until after it commits or aborts.
Rigorous guarantees that a transaction doesn’t release any
of its
locks (including shared locks) until after it commits or
aborts.
64. What is a deadlock?
Ans: Dead lock occurs when each transaction T in a set of
two or
more transactions is waiting for some item that is locked by
some
other transaction T’ in the set. Hence each transaction is
in a
waiting queue, waiting for one of the other transactions to
release
the lock on them.
65. What are triggers?
Ans: Triggers are the PL/SQL blocks definining an action the
database should take when some database related event
occurs.
Triggers may be used to supplement declarative referential
integrity,
to enforce complex business rules, or to audit changes to
data.
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