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Question 1 of 60 Quiz ID: q1

What is the primary purpose of indexing mechanisms in databases?

To reduce storage space requirements

To speed up access to desired data

To improve data security

To compress data files

Question 2 of 60 Quiz ID: q2

What is a search key in the context of database indexing?

A password used to access the database

An encryption key for data security

An attribute or set of attributes used to look up records in a file

A primary key constraint

Question 3 of 60 Quiz ID: q3

An index file consists of records called index entries. What is the typical structure of an index entry?

search-key and pointer

primary key and foreign key

data value and timestamp

record ID and checksum

Question 4 of 60 Quiz ID: q4

What are the two basic kinds of indices mentioned in the lecture?

Primary and secondary indices

Dense and sparse indices

Ordered indices and hash indices

Clustered and non-clustered indices

Question 5 of 60 Quiz ID: q5

Which of the following is NOT mentioned as an index evaluation metric?

Access time

Insertion time

Compression ratio

Space overhead

Question 6 of 60 Quiz ID: q6

In ordered indices, how are index entries stored?

In random order for faster access

Sorted on the search key value

In chronological order of insertion

Grouped by data type

Question 7 of 60 Quiz ID: q7

What is a clustering index?

An index that groups similar records together

An index whose search key specifies the sequential order of the file

An index that uses clustering algorithms

An index distributed across multiple servers

Question 8 of 60 Quiz ID: q8

What is another name for a clustering index?

Secondary index

Primary index

Dense index

Sparse index

Question 9 of 60 Quiz ID: q9

What is a secondary index?

A backup copy of the primary index

An index created after the primary index

An index whose search key specifies an order different from the sequential order of the file

An index with lower priority than the primary index

Question 10 of 60 Quiz ID: q10

What is an index-sequential file?

A file with multiple indices

An ordered sequential file with a primary index

A file stored in sequential order only

A file with hash-based indexing

Question 11 of 60 Quiz ID: q11

What characterizes a dense index?

It has more pointers than records

Index record appears for every search-key value in the file

It uses compression to reduce space

It only indexes frequently accessed records

Question 12 of 60 Quiz ID: q12

In the context of dense indices, what does the example of 'index on ID attribute of instructor relation' illustrate?

How to create composite indices

That every instructor ID has a corresponding index entry

How to handle duplicate keys

The use of hash functions in indexing

Question 13 of 60 Quiz ID: q13

What is a sparse index?

An index with missing or corrupted entries

An index that contains index records for only some search-key values

An index with low storage utilization

An index that uses minimal memory

Question 14 of 60 Quiz ID: q14

When is a sparse index applicable?

When records are randomly distributed

When records are sequentially ordered on search-key

When the file is very small

When fast insertion is required

Question 15 of 60 Quiz ID: q15

To locate a record with search-key value K in a sparse index, what is the procedure?

Find index record with search-key value exactly equal to K

Find index record with largest search-key value < K, then search sequentially

Use binary search on all index entries

Hash the key value K to find the location

Question 16 of 60 Quiz ID: q16

Compared to dense indices, what are the advantages of sparse indices?

Faster record location and better accuracy

Less space and less maintenance overhead for insertions and deletions

Better support for range queries

Higher data integrity and consistency

Question 17 of 60 Quiz ID: q17

What is a disadvantage of sparse indices compared to dense indices?

They require more storage space

They are generally slower for locating records

They cannot handle range queries

They are more complex to implement

Question 18 of 60 Quiz ID: q18

What is recommended as a good tradeoff for sparse indices?

One index entry per record

One index entry for every block in file, corresponding to least search-key value in the block

One index entry per page in memory

One index entry per data type

Question 19 of 60 Quiz ID: q19

Why might a multilevel index be necessary?

To improve data security

If primary index does not fit in memory, making access expensive

To support multiple data types

To enable parallel processing

Question 20 of 60 Quiz ID: q20

In a multilevel index, what is the outer index?

The primary index file

A dense index of all records

A sparse index of the primary index

An index stored in memory

Question 21 of 60 Quiz ID: q21

In a multilevel index, what is the inner index?

A sparse index of the outer index

The primary index file

A hash-based index

A compressed version of the data

Question 22 of 60 Quiz ID: q22

What happens when even the outer index is too large to fit in main memory?

The system crashes

Data must be compressed

Yet another level of index can be created

The file must be reorganized

Question 23 of 60 Quiz ID: q23

What maintenance requirement applies to multilevel indices?

Only the outer index needs updating

Only the inner index needs updating

Indices at all levels must be updated on insertion or deletion

No maintenance is required

Question 24 of 60 Quiz ID: q24

Why might one want secondary indices?

To replace primary indices

To find records based on fields other than the primary index search-key

To improve insertion performance

To reduce storage requirements

Question 25 of 60 Quiz ID: q25

In the instructor relation example, if records are stored sequentially by ID, what would require a secondary index?

Finding instructors by ID

Finding all instructors in a particular department

Inserting new instructor records

Deleting instructor records

Question 26 of 60 Quiz ID: q26

In secondary indices, what does an index record point to when multiple records have the same search-key value?

The first record with that value

A random record with that value

A bucket containing pointers to all actual records with that value

The last record with that value

Question 27 of 60 Quiz ID: q27

Why do secondary indices have to be dense?

To improve performance

Because records are not sequentially ordered on the secondary index search-key

To reduce storage space

To simplify implementation

Question 28 of 60 Quiz ID: q28

What is a major disadvantage of having multiple indices on a file?

Reduced query performance

Updating indices imposes overhead on database modification

Increased storage for data

Complexity in index selection

Question 29 of 60 Quiz ID: q29

Why is sequential scan using a secondary index expensive?

Secondary indices are stored on slow media

Each record access may fetch a new block from disk

Secondary indices have poor compression

They require complex calculations

Question 30 of 60 Quiz ID: q30

According to the lecture, how long does a block fetch typically require compared to memory access?

About the same time

About 5 to 10 milliseconds versus 100 nanoseconds

About 1 second versus 1 millisecond

About 100 times longer

Question 31 of 60 Quiz ID: q31

What is a major disadvantage of indexed-sequential files?

They cannot support range queries

Performance degrades as file grows due to overflow blocks

They require too much memory

They don't support insertions

Question 32 of 60 Quiz ID: q32

What maintenance requirement is problematic for indexed-sequential files?

Daily index updates

Periodic reorganization of the entire file

Frequent memory allocation

Regular backup procedures

Question 33 of 60 Quiz ID: q33

What is a key advantage of B+-tree index files?

They use less storage space

They automatically reorganize with small, local changes

They provide faster sequential access

They eliminate the need for deletion operations

Question 34 of 60 Quiz ID: q34

According to the lecture, do B+-trees require reorganization of the entire file to maintain performance?

Yes, just like indexed-sequential files

No, reorganization of entire file is not required

Only during major updates

Only when the tree becomes unbalanced

Question 35 of 60 Quiz ID: q35

What is a minor disadvantage of B+-trees mentioned in the lecture?

Poor query performance

Extra insertion and deletion overhead, space overhead

Inability to handle large datasets

Complex implementation requirements

Question 36 of 60 Quiz ID: q36

Despite their disadvantages, why are B+-trees used extensively?

They are the only available option

The advantages outweigh the disadvantages

They are required by database standards

They have no maintenance costs

Question 37 of 60 Quiz ID: q37

In hash file organization, what is a bucket?

A hash function parameter

A unit of storage containing one or more records

A type of search key

A backup storage location

Question 38 of 60 Quiz ID: q38

How does hash file organization locate records?

By searching sequentially through all records

By using index entries to point to records

By obtaining the bucket directly from search-key value using a hash function

By sorting records first and then searching

Question 39 of 60 Quiz ID: q39

A hash function h maps from what to what?

Records to search keys

Set of all search-key values K to set of all bucket addresses B

Buckets to records

Indices to data files

Question 40 of 60 Quiz ID: q40

What operations use the hash function in hash file organization?

Only record access

Only insertion and deletion

Access, insertion, and deletion

Only sorting and searching

Question 41 of 60 Quiz ID: q41

Why might an entire bucket need to be searched sequentially in hash file organization?

Buckets are always sorted

Records with different search-key values may be mapped to the same bucket

Hash functions are unreliable

To maintain data integrity

Question 42 of 60 Quiz ID: q42

In the instructor file hash organization example, how many buckets are there?

5 buckets

10 buckets

15 buckets

20 buckets

Question 43 of 60 Quiz ID: q43

In the hash function example, what does h(Music) equal?

Question 44 of 60 Quiz ID: q44

What do h(Physics) and h(Elec. Eng.) both equal in the example?

Question 45 of 60 Quiz ID: q45

What represents the worst possible hash function?

A function that distributes keys evenly

A function that maps all search-key values to the same bucket

A function that uses complex calculations

A function that produces random results

Question 46 of 60 Quiz ID: q46

What characterizes an ideal hash function?

It minimizes computation time

It is uniform - each bucket is assigned the same number of search-key values

It uses simple arithmetic operations

It avoids all collisions

Question 47 of 60 Quiz ID: q47

Why should an ideal hash function be random?

To make it unpredictable for security

To ensure each bucket has the same number of records regardless of actual distribution

To speed up computation

To reduce storage requirements

Question 48 of 60 Quiz ID: q48

What do typical hash functions perform computation on?

The logical representation of search-key

The internal binary representation of the search-key

The ASCII values only

The length of the search-key

Question 49 of 60 Quiz ID: q49

What can cause bucket overflow in hash file organization?

Insufficient buckets and skew in distribution of records

Too many hash functions

Hardware failures

Network congestion

Question 50 of 60 Quiz ID: q50

What are two reasons for skew in distribution of records?

Hardware limitations and software bugs

Multiple records have same search-key value and chosen hash function produces non-uniform distribution

Network delays and disk failures

Memory constraints and CPU limitations

Question 51 of 60 Quiz ID: q51

How is bucket overflow handled in hash file organization?

By increasing the hash table size

By using overflow buckets

By compressing existing records

By rejecting new insertions

Question 52 of 60 Quiz ID: q52

What is overflow chaining?

Linking multiple hash functions together

The overflow buckets of a given bucket are chained together in a linked list

Creating chains of primary buckets

Connecting different hash tables

Question 53 of 60 Quiz ID: q53

What is the overflow chaining scheme called?

Open hashing

Closed hashing

Linear hashing

Dynamic hashing

Question 54 of 60 Quiz ID: q54

Why is open hashing not suitable for database applications?

It is too slow

It does not use overflow buckets

It requires too much memory

It cannot handle concurrent access

Question 55 of 60 Quiz ID: q55

What are bitmap indices designed for?

Compressing large datasets

Efficient querying on multiple keys

Fast sequential access

Reducing storage overhead

Question 56 of 60 Quiz ID: q56

How are records assumed to be organized in bitmap indices?

Randomly distributed

Sorted by primary key

Numbered sequentially from 0

Grouped by data type

Question 57 of 60 Quiz ID: q57

When is record retrieval particularly easy in bitmap indices?

When records are compressed

When records are of fixed size

When records are sorted

When records are encrypted

Question 58 of 60 Quiz ID: q58

Bitmap indices are applicable on attributes that have what characteristic?

Very large number of distinct values

Relatively small number of distinct values

Only numeric values

Only text values

Question 59 of 60 Quiz ID: q59

What is a bitmap in the context of bitmap indices?

A compressed image file

A graphical representation of data

Simply an array of bits

A hash table structure

Question 60 of 60 Quiz ID: q60

In a bitmap for value v, when is the bit for a record set to 1?

When the record is the first occurrence of value v

When the record has the value v for the attribute

When the record was recently accessed

When the record needs to be updated

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