CTS Database Questions
for Degree Students:
1. What is database?
A database is a collection of information that is
organized. So that it can easily be accessed, managed, and updated.
2. What is DBMS?
DBMS stands for Database Management System. It is a collection
of programs that enables user to create and maintain a database.
3. What is a Database system?
The database and DBMS software together is called as Database
system.
4. What are the advantages of DBMS?
I. Redundancy is controlled.
II. Providing multiple user interfaces.
III. Providing backup and recovery
IV. Unauthorized access is restricted.
V. Enforcing integrity constraints.
5. What is normalization?
It is a process of analysing the given relation schemas based on
their Functional Dependencies (FDs) and primary key to achieve the properties
(1).Minimizing redundancy, (2). Minimizing insertion, deletion and update
anomalies.
6. What is Data Model?
A collection of conceptual tools for describing data, data relationships data
semantics and constraints.
7. What is E-R model?
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.
8. What is Object Oriented model?
This model is based on collection of objects. An object contains
values stored in instance variables with in the object. An object also contains
bodies of code that operate on the object. These bodies of code are called
methods. Objects that contain same types of values and the same methods are
grouped together into classes.
9. What is an Entity?
An entity is a thing or object of importance about which data must be
captured.
10. What is DDL (Data Definition Language)?
A data base schema is specifies by a set of definitions
expressed by a special language called DDL.
11. What is DML (Data Manipulation Language)?
This language that enable user to access or manipulate data as
organised by appropriate data model. Procedural DML or Low level: DML
requires a user to specify what data are needed and how to get those data.
Non-Procedural DML or High level: DML requires a user to specify what data are
needed without specifying how to get those data
12. What is DML Compiler?
It translates DML statements in a query language into low-level
instruction that the query evaluation engine can understand.
13. What is Query evaluation engine?
It executes low-level instruction generated by compiler.
14. What is Functional Dependency?
Functional Dependency is the starting point of normalization.
Functional Dependency exists when a relation between two attributes allows you
to uniquely determine the corresponding attribute’s value.
15. What is 1 NF (Normal Form)?
The first normal form or 1NF is the first and the simplest type
of normalization that can be implemented in a database. The main aims of 1NF
are to:
1. Eliminate duplicative columns from the same table.
2. Create separate tables for each group of related data and
identify each row with a unique column (the primary key).
16. What is Fully Functional dependency?
A functional dependency X Y is full functional dependency if
removal of any attribute A from X means that the dependency does not hold any
more.
17. What is 2NF?
A relation schema R is in 2NF if it is in 1NF and every
non-prime attribute A in R is fully functionally dependent on primary key.
18. What is 3NF?
A relation is in third normal form if it is in Second Normal
Form and there are no functional (transitive) dependencies between two (or
more) non-primary key attributes.
19. What is BCNF (Boyce-Codd Normal Form)?
A table is in Boyce-Codd normal form (BCNF) if and only if it is
in 3NF and every determinant is a candidate key.
20. What is 4NF?
Fourth normal form requires that a table be BCNF and contain no
multi-valued dependencies.
21. What is 5NF?
A table is in fifth normal form (5NF) or Project-Join Normal
Form (PJNF) if it is in 4NF and it cannot have a lossless decomposition into
any number of smaller tables.
22. What is a query?
A query with respect to DBMS relates to user commands that are
used to interact with a data base.
23. What is meant by query optimization?
The phase that identifies an efficient execution plan for
evaluating a query that has the least estimated cost is referred to as query
optimization.
24. What is an attribute?
It is a particular property, which describes the entity.
25. What is RDBMS?
Relational Data Base Management Systems (RDBMS) are database
management systems that maintain data records and indices in tables.
26. What’s
difference between DBMS and RDBMS?
DBMS provides a systematic and organized way of storing,
managing and retrieving from collection of logically related information. RDBMS
also provides what DBMS provides but above that it provides relationship
integrity.
27. What is SQL?
SQL stands for Structured Query Language. SQL is an ANSI
(American National Standards Institute) standard computer language for
accessing and manipulating database systems. SQL statements are used to
retrieve and update data in a database.
28. What is Stored Procedure?
A stored procedure is a named group of SQL statements that have
been previously created and stored in the server database.
29. What is a view?
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.
30. What is Trigger?
A trigger is a SQL procedure that initiates an action when an
event (INSERT, DELETE or UPDATE) occurs.
31. What is Index?
An index is a physical structure containing pointers to the
data.
32. What is extension and intension?
Extension -It is the number of tuples present in a table at any
instance. This is time dependent.
Intension -It is a constant value that gives the name, structure
of table and the constraints laid on it.
33. What do you mean by atomicity and aggregation?
Atomicity-Atomicity states that database modifications must
follow an “all or nothing” rule. Each
transaction is said to be “atomic.” If one part of the transaction
fails, the entire transaction fails.
Aggregation - A feature of the entity relationship model that
allows a relationship set to participate in another relationship set. This is
indicated on an ER diagram by drawing a dashed box around the aggregation.
34. What is RDBMS KERNEL?
Two important pieces of RDBMS architecture are the kernel, which
is the software, and the data dictionary, which consists of the system- level
data structures used by the kernel to manage the database.
35. Name the sub-systems of a RDBMS?
I/O, Security, Language Processing, Process Control,
Storage Management, Logging and Recovery, Distribution
Control, Transaction Control, Memory Management, Lock Management.
36. How do you communicate with an RDBMS?
You communicate with an RDBMS using Structured Query Language
(SQL)
37. Disadvantage in File Processing System?
· Data redundancy
& inconsistency.
· Difficult in
accessing data.
· Data isolation.
· Data integrity.
· Concurrent access is
not possible.
· Security Problems.
38. What is VDL (View Definition Language)?
It specifies user views and their mappings to the conceptual
schema.
39. What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This language
may Specify the mapping between two schemas.
40. Describe concurrency control?
Concurrency control is the process managing simultaneous
operations against a database so that database integrity is no compromised.
There are two approaches to concurrency control.
The pessimistic approach involves locking and the optimistic
approach involves versioning.
41. Describe the difference between homogeneous and
heterogeneous distributed database?
A homogenous database is one that uses the same DBMS at each
node. A heterogeneous database is one that may have a different DBMS at each
node.
42. What is a distributed database?
A distributed database is a single logical database that is
spread across more than one node or locations that are all connected via some
communication link.
43. Explain the difference between two and three-tier
architectures?
Three-tier architecture includes a client and two server layers.
The application code is stored on the application
server and the database is stored on the database server. A
two-tier architecture includes a client and one server layer. The database is
stored on the database server.
44. Briefly describe the three types of SQL commands?
Data definition language commands are used to create, alter, and
drop tables. Data manipulation commands are used to insert, modify, update, and
query data in the database. Data control language commands help the DBA to
control the database.
45. List some of the properties of a relation?
Relations in a database have a unique name and no multivalued
attributes exist. Each row is unique and each attribute within a relation has a
unique name. The sequence of both columns and rows is irrelevant.
46. Explain the differences between an intranet and an extranet?
An Internet database is accessible by everyone who has access to
a Web site. An intranet database limits access to only people within a given
organization.
47. What is SQL Deadlock?
Deadlock is a unique situation in a multi user system that causes
two or more users to wait indefinitely for a locked resource.
48. What is a Catalog?
A catalog is a table that contains 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.
49. What is data ware housing & OLAP?
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 .
50. Describe the three levels of data abstraction?
Physical level: The lowest level of abstraction describes how
data are stored.
Logical level: The next higher level of abstraction, describes
what data are stored in database and what relationship among those data.
View level: The highest level of abstraction describes only part
of entire database.
51. What is Data Independence?
Data independence means that the application is independent of
the storage structure and access strategy of data.
52. How many types of relationship exist in database designing?
There are three major relationship models:-
One-to-one
One-to-many
Many-to-many
53. What is order by clause?
ORDER BY clause helps to sort the data in either ascending order
to descending
54. What is the use of DBCC commands?
DBCC stands for database consistency checker. We use these
commands to check the consistency of the databases, i.e.,
maintenance, validation task and status checks.
55. What is Collation?
Collation refers to a set of rules that determine how data is
sorted and compared.
56. What is difference between DELETE & TRUNCATE commands?
Delete command removes the rows from a table based on the
condition that we provide with a WHERE clause. Truncate will actually remove
all the rows from a table and there will be no data in the table after we run
the truncate command.
57. What is Hashing technique?
This is a primary file organization technique that provides very
fast access to records on certain search conditions.
58. What is a transaction?
A transaction is a logical unit of database processing that
includes one or more database access operations.
59. What are the different phases of Transaction?
Analysis phase
Redo phase
Undo phase
60. What is “transparent
dbms”?
It is one, which keeps its physical structure hidden from user.
61. What are the primitive operations common to all record
management System?
Addition, deletion and modification.
62. Explain the differences between structured data and
unstructured data.
Structured data are facts concerning objects and events. The
most important structured data are numeric, character, and dates.
Structured data are stored in tabular form. Unstructured data
are multimedia data such as documents, photographs, maps, images, sound, and
video clips. Unstructured data are most commonly found on Web servers and
Web-enabled databases.
63. What are the major functions of the database administrator?
Managing database structure, controlling concurrent processing,
managing processing rights and responsibilities, developing database security,
providing for database recovery, managing the DBMS and maintaining the data
repository.
64. What is a dependency graph?
A dependency graph is a diagram that is used to portray the
connections between database elements.
65. Explain the difference between an exclusive lock and a
shared lock?
An exclusive lock prohibits other users from reading the locked
resource; a shared lock allows other users to read the locked resource, but
they cannot update it.
66. Explain the "paradigm mismatch" between SQL and
application programming languages.
SQL statements return a set of rows, while an application
program works on one row at a time. To resolve this mismatch the results of
SQL statements are processed as pseudofiles, using a cursor or pointer to
specify which row is being processed.
67. Name four applications for triggers.
(1)Providing default values, (2) enforcing data constraints,
(3) Updating views and (4) enforcing referential integrity
68. What are the advantages of using stored procedures?
The advantages of stored procedures are (1) greater security,
(2) decreased network traffic, (3) the fact that SQL can be optimized and (4)
code sharing which leads to less work, standardized processing, and
specialization among developers.
69. Explain the difference between attributes and identifiers.
Entities have attributes. Attributes are properties that
describe the entity's characteristics. Entity instances have identifiers.
Identifiers are attributes that name, or identify, entity instances.
70. What is Enterprise Resource Planning (ERP), and what kind of
a database is used in an ERP application?
Enterprise Resource Planning (ERP) is an information system used
in manufacturing companies and includes sales, inventory, production planning,
purchasing and other business functions. An ERP system typically uses a
multiuser database.
71. Describe the difference between embedded and dynamic SQL?
Embedded SQL is the process of including hard coded SQL
statements. These statements do not change unless the source code is modified.
Dynamic SQL is the process of generating SQL on the fly.The statements
generated do not have to be the same each time.
72. Explain a join between tables
A join allows tables to be linked to other tables when a
relationship between the tables exists. The relationships are established by
using a common column in the tables and often uses the primary/foreign key
relationship.
73. Describe a subquery.
A subquery is a query that is composed of two queries. The first
query (inner query) is within the WHERE clause of the other query (outer
query).
74. Compare a hierarchical and network database model?
The hierarchical model is a top-down structure where each parent
may have many children but each child can have only one parent. This model
supports one-to-one and one-to-many relationships.
The network model can be much more flexible than the
hierarchical model since each parent can have multiple children but each child
can also have multiple parents. This model supports one-to-one, one-to-many,
and many-to-many relationships.
75. Explain the difference between a dynamic and materialized
view.
A dynamic view may be created every time that a specific view is
requested by a user. A materialized view is created and or updated infrequently
and it must be synchronized with its associated base table(s).
76. Explain what needs to happen to convert a relation to third
normal form.
First you must verify that a relation is in both first normal
form and second normal form. If the relation is not, you must convert into
second normal form. After a relation is in second normal form, you must remove
all transitive dependencies.
77. Describe the four types of indexes?
A unique primary index is unique and is used to find and store a
row. A nonunique primary index is not unique and is used to find a row but also
where to store a row (based on its unique primary index). A unique secondary
index is unique for each row and used to find table rows. A nonunique secondary
index is not unique and used to find table rows.
78. Explain minimum and maximum cardinality?
Minimum cardinality is the minimum number of instances of an
entity that can be associated with each instance of another entity.
Maximum cardinality is the maximum number of instances of an entity that
can be associated with each instance of another entity.
79. What is deadlock? How can it be avoided? How can it be
resolved once it occurs?
Deadlock occurs when two transactions are each waiting on a
resource that the other transaction holds. Deadlock can be prevented by
requiring transactions to acquire all locks at the same time; once it occurs,
the only way to cure it is to abort one of the transactions and back out of
partially completed work.
80. Explain what we mean by an ACID transaction.
An ACID transaction is one that is atomic, consistent, isolated,
and durable. Durable means that database changes are permanent. Consistency can
mean either statement level or transaction level consistency. With transaction
level consistency, a transaction may not see its own changes.Atomic means it is
performed as a unit.
81. Under what conditions should indexes be used?
Indexes can be created to enforce uniqueness, to facilitate
sorting, and to enable fast retrieval by column values. A good candidate for an
index is a column that is frequently used with equal conditions in WHERE
clauses.
82. What is difference between SQL and SQL SERVER?
SQL is a language that provides an interface to RDBMS, developed
by IBM. SQL SERVER is a RDBMS just like Oracle, DB2.
83. What is Specialization?
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.
84. What is generalization?
It is the process of finding common attributes and relations of
a number of entities and defining a common super class for them.
85. What is meant by Proactive, Retroactive and Simultaneous
Update?
Proactive Update: The updates that are applied to database
before it becomes effective in real world.
Retroactive Update: The updates that are applied to database
after it becomes effective in real world.
Simultaneous Update: The updates that are applied to database at
the same time when it becomes effective in real world.
86. What is RAID Technology?
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.
87. What are serial, non serial schedule?
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.
88. What are conflict serializable schedules?
A schedule S of n transactions is serializable if it is
equivalent to some serial schedule of the same n transactions.
89. What is view serializable?
A schedule is said to be view serializable if it is view
equivalent with some serial schedule.
90. What is a foreign key?
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.
91. What are the disadvantages of using a dbms?
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.
92. What is Lossless join property?
It guarantees that the spurious tuple generation does not occur with respect to
relation schemas after decomposition.
93. What is a Phantom Deadlock?
In distributed deadlock detection, the delay in propagating local information
might cause the deadlock detection algorithms to identify deadlocks that do not
really exist. Such situations are called phantom deadlocks and they lead to
unnecessary aborts.
94. What is a checkpoint and When does it occur?
A Checkpoint is like a snapshot of the DBMS state. By taking checkpoints, the
DBMS can reduce the amount of work to be done during restart in the event of
subsequent crashes.
95. What is schema?
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.
