DATABASE MANAGEMENT SYSTEMS
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UNIT I
PART A
1. Define database management system?
Database management system (DBMS) is a collection of interrelated data and a
Set of programs to access those data.
2. List few 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
3. 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
4. What are the advantages of using a DBMS?
The advantages of using a DBMS are
a) Controlling redundancy
b) Restricting unauthorized access
c) Providing multiple user interfaces
d) Enforcing integrity constraints.
e) Providing back up and recovery
5. Give the levels of data abstraction?
a) Physical level
b) logical level
c) view level
6. 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.
7. 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.
8. What is conceptual schema?
The schemas at the view level are called subschemas that describe different views
of the database.
9. Define data model?
A data model is a collection of conceptual tools for describing data, data
relationships, data semantics and consistency constraints.
10. 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.
11. 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
12. What is the purpose of storage manager?
The storage manager is responsible for the following
a) Interaction with he file manager
b) Translation of DML commands in to low level file system commands
c) Storing, retrieving and updating data in the database
13. 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
14. 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.
15. 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.
16. 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.
17. 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.
18. Define the terms
i) Entity set
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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.
19. 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.
20. 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.
21. What are composite attributes?
Composite attributes can be divided in to sub parts.
22. 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.
23. 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.
24. What is meant by the degree of relationship set?
The degree of relationship type is the number of participating entity types.
25. 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.
26. 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.
27. 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
28. 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.
29. 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.
30. 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.
31. Define tuple and attribute
• Attributes: column headers
• Tuple: Row
32. Define the term relation.
Relation is a subset of a Cartesian product of list domains.
33. Define tuple variable
Tuple variable is a variable whose domain is the set of all tuples.
UNIT 2
PART A
1. What are the parts of SQL language?
The SQL language has several parts:
data -definitition language
Data manipulation language
View definition
Transaction control
Embedded SQL
Integrity
Authorization
2. What are the categories of SQL command?
SQL commands are divided in to the following categories:
1. data -definitition language
2. data manipulation language
3. Data Query language
4. data control language
5. data administration statements
6. transaction control statements
3. What are the three classes of SQL expression?
SQL expression consists of three clauses:
Select From where
4. Give the general form of SQL query?
Select A1, A2............., An
From R1, R2..............., Rm Where P
5. What is the use of rename operation?
Rename operation is used to rename both relations and a attributes.
It uses the as clause, taking the form:
Old-name as new-name
6. 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.
7. 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.
8. List the set operations of SQL?
1) Union
2) Intersect operation
3) The except operation
9. 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.
10. 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
11. What is the use of group by clause?
Group by clause is used to apply aggregate functions to a set of tuples.The
attributes given in the group by clause are used to form groups.Tuples with the
same value on all attributes in the group by clause are placed in one group.
12. What is the use of sub queries?
A sub query is a select-from-where expression that is nested with in another
query. A common use of sub queries is to perform tests for set membership, make
setcomparisions, and determine set cardinality.
13. What is view in SQL? How is it defined?
Any relation that is not part of the logical model, but is made visible to a user as a
virtual relation is called a view.
We define view in SQL by using the create view command. The form of the
create view command is
Create view v as <query expression>
14. What is the use of with clause in SQL?
The with clause provides a way of defining a temporary view whose definition is
available only to the query in which the with clause occurs.
15. List the table modification commands in SQL?
Deletion
Insertion
Updates
Update of a view
16. List out the statements associated with a database transaction?
Commit work
Rollback work
17. What is transaction?
Transaction is a unit of program execution that accesses and possibly updated
various data items.
18. List the SQL domain Types?
SQL supports the following domain types.
1) Char(n) 2) varchar(n) 3) int 4) numeric(p,d)
5) float(n) 6) date.
19. What is the use of integrity constraints?
Integrity constraints ensure that changes made to the database by authorized users
do not result in a loss of data consistency. Thus integrity constraints guard against
accidental damage to the database.
20. Mention the 2 forms of integrity constraints in ER model?
Key declarations
Form of a relationship
21. What is trigger?
Triggers are statements that are executed automatically by the system as the side
effect of a modification to the database.
22. What are domain constraints?
A domain is a set of values that may be assigned to an attribute .all values that
appear in a column of a relation must be taken from the same domain.
23. What are referential integrity constraints?
A value that appears in one relation for a given set of attributes also appears for a
certain set of attributes in another relation.
24. What is assertion? Mention the forms available.
An assertion is a predicate expressing a condition that we wish the database
always to satisfy.
Domain integrity constraints.
Referential integrity constraints
25. Give the syntax of assertion?
Create assertion <assertion name>check<predicate>
26. What is the need for triggers?
Triggers are useful mechanisms for alerting humans or for starting certain tasks
automatically when certain conditions are met.
27. List the requirements needed to design a trigger.
The requirements are
Specifying when a trigger is to be executed.
Specify the actions to be taken when the trigger executes.
28. Give the forms of triggers?
The triggering event can be insert or delete.
For updated the trigger can specify columns.
The referencing old row as clause
The referencing new row as clause
The triggers can be initiated before the event or after the event.
29. What does database security refer to?
Database security refers to the protection from unauthorized access and malicious
destruction or alteration.
30. List some security violations (or) name any forms of malicious access.
Unauthorized reading of data
Unauthorized modification of data
Unauthorized destruction of data.
31. List the types of authorization.
Read authorization
Write authorization
Update authorization
Drop authorization
32. What is authorization graph?
Passing of authorization from one user to another can be represented by an
authorization graph.
33. List out various user authorization to modify the database schema.
Index authorization
Resource authorization
Alteration authorization
Drop authorization
34. What are audit trails?
An audit trail is a log of all changes to the database along with information such
as which user performed the change and when the change was performed.
35. Mention the various levels in security measures.
Database system
Operating system
Network
Physical
human
36. Name the various privileges in SQL?
Delete
Select
Insert
update
37. Mention the various user privileges.
All privileges directly granted to the user or role.
All privileges granted to roles that have been granted to the user or role.
38. Give the limitations of SQL authorization.
The code for checking authorization becomes intermixed with the rest of the
application code.
Implementing authorization through application code rather than specifying it
declaratively in SQL makes it hard to ensure the absence of loopholes.
39. Define the term Domain.
For each attribute there is a set of permitted values called the domain of that
attribute.
40. What is a candidate key?
Minimal super keys are called candidate keys.
41. 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.
42. 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.
43. Define-relational algebra.
The relational algebra is a procedural query language. It consists of a set of
operations that take one or two relation as input and produce a new relation as
output.
44. What is a SELECT operation?
The select operation selects tuples that satisfy a given predicate. We use the
lowercase letter sssss to denote selection.
45. 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 (p
pppp).
46. 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.
47. 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.
48. Give some encryption techniques?
DES
AES
Public key encryption
49. What does authentication refer?
Authentication refers to the task of verifying the identity of a person.
50. List some authentication techniques.
Challenge response scheme
Digital signatures
Nonrepudiation
UNIT III
1. Define Boyce codd normal form
A relation schema R is in BCNF with respect to a set F of functional
+dependencies if, for all functional dependencies in F of the form
2. List the disadvantages of relational database system
Repetition of data
Inability to represent certain information.
3. What is first normal form?
The domain of attribute must include only atomic (simple, indivisible) values.
4. What is meant by functional dependencies?
Consider a relation schema R and a
C
R and ß
C
R. The functional dependency a
ß
holds on relational schema R if in any legal relation r(R), for all pairs of
tuples t1 and t2 in r such that t1 [] =t1 [], and also t1 [[1]] =t2 [[1]].
5. What are the uses of functional dependencies?
To test relations to see whether they are legal under a given set of functional
dependencies.
To specify constraints on the set of legal relations.
6. Explain trivial dependency?
Functional dependency of the form a
ß
is trivial if ß
C
. Trivial functional
dependencies are satisfied by all the relations.
7. What are axioms?
Axioms or rules of inference provide a simpler technique for reasoning about
functional dependencies.
8. What is meant by computing the closure of a set of functional dependency?
The closure of F denoted by F+ is the set of functional dependencies logically
implied by F.
9. What is meant by normalization of data?
It is a process of analyzing the given relation schemas based on their Functional
Dependencies (FDs) and primary key to achieve the properties
Minimizing redundancy
Minimizing insertion, deletion and updating anomalies.
10. Define canonical cover?
A canonical cover Fc for F is a set of dependencies such that F logically implies
all dependencies in FC and Fc logically implies all dependencies in F. Fc must
have the following properties.
11. List the properties of canonical cover.
Fc must have the following properties.
No functional dependency in Fc contains an extraneous attribute.
Each left side of a functional dependency in Fc is unique.
12. Explain the desirable properties of decomposition.
Lossless-join decomposition
Dependency preservation
Repetition of information
13. 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.
14.Define 1NF
• Tabular format in which:
• All key attributes are defined
• There are no repeating groups in the table
• All attributes are dependent on primary key
• All relational tables must satisfy 1NF requirements
15. How to convert to First Normal Form
A table in a relational database must be in 1NF.
• Repeating groups must be eliminated
• Primary key determined
• Uniquely identify attribute values (rows)
• All attributes dependent on primary key
• In example: Combination of PROJ_NUM and EMP_NUM
16.What is Dependency diagram?
• Dependency diagram:
• Depicts all dependencies found within a given table structure
• Helpful in getting bird’s-eye view of all relationships among a table’s attributes
• Use makes it much less likely that an important dependency will be overlooked
17.What are the Desirable dependencies based on entire primary key
Partial:
Based on part of composite primary key
Transitive:
One nonprime attribute depends on another nonprime attribute
18.What are the aspects to be considered to check Table is in second normal form (2NF)?
Table is in second normal form (2NF) if:
ü It is in 1NF and
ü It includes no partial dependencies:
ü No attribute is dependent on only a portion of the primary key
19.Define Physical Data Independence:
The execution of application programs is not affected by the changes in the physical
data access and storage methods.
20.Define Logical Data Independence:
Logical changes in tables and views such as adding/deleting columns or changing field
length need not necessiatitate modifications in the programs. The database can change and
grow to reflect changes in reality without requiring the user intervention or changes in the
applications.
UNIT IV
PART A
1. What is transaction?
Collections of operations that form a single logical unit of work are called
transactions.
2. What are the two statements regarding transaction?
The two statements regarding transaction of the form:
.Begin transaction
.End transaction
3. What are the properties of transaction?
The properties of transactions are:
.Atomicity
.Consistency
.Isolation
.Durability
4. What is recovery management component?
Ensuring durability is the responsibility of a software component of the base
system called the recovery management component.
5. When is a transaction rolled back?
Any changes that the aborted transaction made to the database must be undone.
Once the changes caused by an aborted transaction have been undone, then the
transaction has been rolled back.
6. What are the states of transaction?
The states of transaction are
. Active
. Partially committed
. Failed
. Aborted
.Committed
.Terminated
7. What is a shadow copy scheme?
It is simple, but efficient, scheme called the shadow copy schemes. It is based on
making copies of the database called shadow copies that one transaction is active at a
time. The scheme also assumes that the database is simply a file on disk.
8. Give the reasons for allowing concurrency?
The reasons for allowing concurrency is if the transactions run serially, a short
transaction may have to wait for a preceding long transaction to complete, which can lead
to unpredictable delays in running a transaction.
So concurrent execution reduces the unpredictable delays in running transactions.
9. What is average response time?
The average response time is that the average time for a transaction to be
completed after it has been submitted.
10. What are the two types of serializability?
The two types of serializability is
. Conflict serializability
. View serializability
11. Define lock?
Lock is the most common used to implement the requirement is to allow a
transaction to access a data item only if it is currently holding a lock on that item.
12. What are the different modes of lock?
The modes of lock are:
.Shared
.Exclusive
13. Define deadlock?
Neither of the transaction can ever proceed with its normal execution. This
situation is called deadlock.
14. Define the phases of two phase locking protocol
. Growing phase: a transaction may obtain locks but not release any lock.
.Shrinking phase: a transaction may release locks but may not obtain any new
locks.
15. Define upgrade and downgrade?
It provides a mechanism for conversion from shared lock to exclusive lock is
known as upgrade.
It provides a mechanism for conversion from exclusive lock to shared lock is
known as downgrade.
16. What is a database graph?
The partial ordering implies that the set D may now be viewed as a directed
acyclic graph, called a database graph.
17. What are the two methods for dealing deadlock problem?
The two methods for dealing deadlock problem is deadlock detection and
deadlock recovery.
18. What is a recovery scheme?
An integral part of a database system is a recovery scheme that can restore the
database to the consistent state that existed before the failure.
19. What are the two types of errors?
The two types of errors are:
. Logical error
. System error
20. What are the storage types?
The storage types are:
. Volatile storage
. Nonvolatile storage
21. Define blocks?
The database system resides permanently on nonvolatile storage, and is
partitioned into fixed-length storage units called blocks.
22. What is meant by Physical blocks?
The input and output operations are done in block units. The blocks residing on
the disk are referred to as physical blocks.
23. What is meant by buffer blocks?
The blocks residing temporarily in main memory are referred to as buffer blocks.
24. What is meant by disk buffer?
The area of memory where blocks reside temporarily is called the disk buffer.
25. What is meant by log-based recovery?
The most widely used structures for recording database modifications is the log.
The log is a sequence of log records, recording all the update activities in the database.
There are several types of log records.
26. What are uncommitted modifications?
The immediate-modification technique allows database modifications to be output
to the database while the transaction is still in the active state. Data modifications written
by active transactions are called uncommitted modifications.
27. Define shadow paging.
An alternative to log-based crash recovery technique is shadow paging. This
technique needs fewer disk accesses than do the log-based methods.
28. Define page.
The database is partitioned into some number of fixed-length blocks, which are
referred to as pages.
29. Explain current page table and shadow page table.
The key idea behind the shadow paging technique is to maintain two page tables
during the life of the transaction: the current page table and the shadow page table. Both
the page tables are identical when the transaction starts. The current page table may be
changed when a transaction performs a write operation.
30. What are the drawbacks of shadow-paging technique?
•Commit Overhead
•Data fragmentation
•Garbage collection
30. Define garbage collection.
Garbage may be created also as a side effect of crashes. Periodically, it is
necessary to find all the garbage pages and to add them to the list of free pages. This
process is called garbage collection.
32. Differentiate strict two phase locking protocol and rigorous two phase locking
protocol.
In strict two phase locking protocol all exclusive mode locks taken by a
transaction is held until that transaction commits. Rigorous two phase locking protocol requires
that all locks be held until the transaction commits.
33. How the time stamps are implemented
•Use the value of the system clock as the time stamp. That is a transaction’s
time stamp is equal to the value of the clock when the transaction enters the
system.
•Use a logical counter that is incremented after a new timestamp has been
assigned; that is the time stamp is equal to the value of the counter.
34. What are the time stamps associated with each data item?
• W-timestamp (Q) denotes the largest time stamp if any transaction that
executed WRITE (Q) successfully.
• R-timestamp (Q) denotes the largest time stamp if any transaction that
executed READ (Q) successfully.
UNIT V
PART A
1. Give the measures of quality of a disk.
Capacity
Access time
Seek time
Data transfer rate
Reliability
Rotational latency time.
2. Compare sequential access devices versus random access devices with an example
sequential access devices random access devices
Must be accessed from the beginning It is possible to read data from any location
Eg:-tape storage Eg:-disk storage
Access to data is much slower Access to data is faster
Cheaper than disk Expensive when compared with disk
3. What are the types of storage devices?
Primary storage
Secondary storage
Tertiary storage
4. Draw the storage device hierarchy according to their speed and their cost.
Cache
Main memory
Flash memory
Magnetic disk
Optical disk
Magnetic tapes
5. What are called jukebox systems?
Jukebox systems contain a few drives and numerous disks that can be loaded into
one of the drives automatically.
6. What is called remapping of bad sectors?
If the controller detects that a sector is damaged when the disk is initially
formatted, or when an attempt is made to write the sector, it can logically map the sector
to a different physical location.
7. Define access time.
Access time is the time from when a read or write request is issued to when data
transfer begins.
8. Define seek time.
The time for repositioning the arm is called the seek time and it increases with the
distance that the arm is called the seek time.
9. Define average seek time.
The average seek time is the average of the seek times, measured over a sequence
of random requests.
10. Define rotational latency time.
The time spent waiting for the sector to be accessed to appear under the head is
called the rotational latency time.
11. Define average latency time.
The average latency time of the disk is one-half the time for a full rotation of the
disk.
12. What is meant by data-transfer rate?
The data-transfer rate is the rate at which data can be retrieved from or stored to
the disk.
13. What is meant by mean time to failure?
The mean time to failure is the amount of time that the system could run
continuously without failure.
14. What are a block and a block number?
A block is a contiguous sequence of sectors from a single track of one platter.
Each request specifies the address on the disk to be referenced. That address is in the
form of a block number.
15. What are called journaling file systems?
File systems that support log disks are called journaling file systems.
16. What is the use of RAID?
A variety of disk-organization techniques, collectively called redundant arrays of
independent disks are used to improve the performance and reliability.
17. Explain how reliability can be improved through redundancy?
The simplest approach to introducing redundancy is to duplicate every disk. This
technique is called mirroring or shadowing. A logical disk then consists of two physical
disks, and write is carried out on both the disk. If one of the disks fails the data can be
read from the other. Data will be lost if the second disk fails before the first fail ed disk is
repaired.
18. What is called mirroring?
The simplest approach to introducing redundancy is to duplicate every disk. This
technique is called mirroring or shadowing.
19. What is called mean time to repair?
The mean time to failure is the time it takes to replace a failed disk and to restore
the data on it.
20. What is called bit-level striping?
Data striping consists of splitting the bits of each byte across multiple disks. This
is called bit-level striping.
21. What is called block-level striping?
Block level striping stripes blocks across multiple disks. It treats the array of disks
as a large disk, and gives blocks logical numbers.
22. What are the two main goals of parallelism?
Load –balance multiple small accesses, so that the throughput of such
accesses increases.
Parallelize large accesses so that the response time of large accesses is
reduced
23. What are the factors to be taken into account when choosing a RAID level?
Monetary cost of extra disk storage requirements.
Performance requirements in terms of number of I/O operations
Performance when a disk has failed.
Performances during rebuild.
24. What is meant by software and hardware RAID systems?
RAID can be implemented with no change at the hardware level, using only
software modification. Such RAID implementations are called software RAID systems
and the systems with special hardware support are called hardware RAID systems.
25. Define hot swapping?
Hot swapping permits the removal of faulty disks and replaces it by new ones
without turning power off. Hot swapping reduces the mean time to repair.
26. Which level of RAID is best? Why?
RAID level 1 is the RAID level of choice for many applications with moderate
storage requirements and high I/O requirements. RAID 1 follows mirroring and provides
best write performance.
27. Distinguish between fixed length records and variable length records?
Fixed length records
Every record has the same fields and field lengths are fixed.
Variable length records
File records are of same type but one or more of the fields are of varying size.
28. What are the ways in which the variable-length records arise in database
systems?
Storage of multiple record types in a file.
Record types that allow variable lengths for one or more fields.
Record types that allow repeating fields.
29. Explain the use of variable length records.
They are used for Storing of multiple record types in a file.
Used for storing records that has varying lengths for one or more fields.
Used for storing records that allow repeating fields
30. What is the use of a slotted-page structure and what is the information present
in the header?
The slotted-page structure is used for organizing records within a single block.
The header contains the following information.
The number of record entries in the header.
The end of free space
An array whose entries contain the location and size of each record.
31. What are the two types of blocks in the fixed –length representation? Define
them.
Anchor block: Contains the first record of a chain.
Overflow block: Contains the records other than those that are the first
record of a chain.
32. What is known as heap file organization?
In the heap file organization, any record can be placed anywhere in the file where
there is space for the record. There is no ordering of records. There is a single file for
each relation.
33. What is known as sequential file organization?
In the sequential file organization, the records are stored in sequential order,
according to the value of a “search key” of each record.
34. What is hashing file organization?
In the hashing file organization, a hash function is computed on some attribute of
each record. The result of the hash function specifies in which block of the file the record
should be placed.
35. What is known as clustering file organization?
In the clustering file organization, records of several different relations are stored
in the same file.
36. What is an index?
An index is a structure that helps to locate desired records of a relation quickly,
without examining all records.
37. What are the two types of ordered indices?
. Primary index
. Secondary index
38. What are the types of indices?
.Ordered indices
.Hash indices
39. What are the techniques to be evaluated for both ordered indexing and hashing?
.Access types
.Access time
.Insertion time
.Deletion time
.Space overhead
40. What is known as a search key?
An attribute or set of attributes used to look up records in a file is called a search
key.
41. What is a primary index?
A primary index is an index whose search key also defines the sequential order of
the file.
42. What are called index-sequential files?
The files that are ordered sequentially with a primary index on the search key are
called index-sequential files.
43. What are the two types of indices?
.Dense index
.Sparse index
44. What are called multilevel indices?
Indices with two or more levels are called multilevel indices.
45. What are called secondary indices?
Indices whose search key specifies an order different from sequential order of the
file are called secondary indices. The pointers in secondary index do not point directly to
the file. Instead each points to a bucket that contains pointers to the file.
46. What are the disadvantages of index sequential files?
The main disadvantage of the index sequential file organization is that
performance degrades as the file grows. This degradation is remedied by reorganization
of the file.
47. What is a B+-Tree index?
A B+-Tree index takes the form of a balanced tree in which every path from the
root of the root of the root of the tree to a leaf of the tree is of the same length.
P1 K1 P2 K2 ............. Pn-1 Kn-1 Pn
A node contains up to n-1 search key values and n pointers.
48. What is B-Tree?
A B-tree eliminates the redundant storage of search-key values .It allows search
key values to appear only once.
49. What is hashing?
Hashing allows us to find the address of a data item directly by computing a hash
function on the search key value of the desired record.
50. How do you create index in SQL?
We create index by he create index command.
Create index<index name>on <relation name> (<attribute list>)
51. Distinguish between static hashing and dynamic hashing?
Static hashing
Static hashing uses a hash function in which the set of bucket adders is
fixed. Such hash functions cannot easily accommodate databases that
grow larger over time.
Dynamic hashing
Dynamic hashing allows us to modify the hash function dynamically.
Dynamic hashing copes with changes in database size by splitting and
coalescing buckets as the database grows and shrinks.
52. What is a hash index?
A hash index organizes the search keys, with their associated pointers, into a hash
file structure.
53. What can be done to reduce the occurrences of bucket overflows in a hash file
organization?
.To reduce bucket overflow the number of bucket is chosen to be
(nr/fr)*(1+d).
.We handle bucket overflow by using
•Overflow chaining(closed hashing)
•Open hashing
54. Differentiate open hashing and closed hashing (overflow chaining)
Closed hashing (overflow chaining)
If a record must be inserted in to a bucket b, and b is already full, the system
provides an overflow bucket for b, and inserts the record in to the overflow bucket. If the
overflow bucket is also full, the system provides another overflow bucket, and so on. All
the overflow buckets of a given buckets are chained together in a linked list, overflow
handling using linked list is known as closed hashing.
Open hashing
The set of buckets is fixed, and there are no overflow chains. Instead, if a bucket
is full, the system inserts records in some other bucket in the initial set of buckets.
55. What is linear probing?
Linear probing is a type of open hashing. If a bucket is full the system inserts
records in to the next bucket that has space. This is known as linear probing.
56. What is called query processing?
Query processing refers to the range of activities involved in extracting data from
a database.
57. What are the steps involved in query processing?
The basic steps are:
.parsing and translation .optimization
.evaluation
58. What is called an evaluation primitive?
A relational algebra operation annotated with instructions on how to evaluate is
called an evaluation primitive.
59. What is called a query evaluation plan?
A sequence of primitive operations that can be used to evaluate ba query is a
query evaluation plan or a query execution plan.
60. What is called a query –execution engine?
The query execution engine takes a query evaluation plan, executes that plan, and
returns the answers to the query.
61. How do you measure the cost of query evaluation?
The cost of a query evaluation is measured in terms of a number of different
resources including disk accesses, CPU time to execute a query, and in a distributed
database system the cost of communication
62. List out the operations involved in query processing
Selection operation
Join operations.
Sorting.
Projection
Set operations
Aggregation
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