CS 6400 Exam 4 Complete Questions And 100%
Verified Answers Brand New Version Graded
A+
Multilevel index -- B+ tree - {✔✔Resolution Result Verified Answers ✔✔}-
Insertion, deletion, and update operations are implemented to keep the tree
balanced
Only rarely does an overflow at a lower level of the tree propagate more than 1-2
levels up
Static Hashing - {✔✔Resolution Result Verified Answers ✔✔}-You have a
very large space of key values
(for example: Email addresses of regular users)
Hash function h Job of the hash function is to take keys from the key value space
and match them into an address in a bucket directory
Good hash function properties - {✔✔Resolution Result Verified Answers
✔✔}-Distribute values uniformly over the address space
Fill buckets as much as possible because it takes more than just a few blocks, and
therefore needs to be stored somewhere and therefore a piece of it might be
stored on disk and itself be subject to being ported between disk and memory
,Avoid collisions -- Collisions occur when the hash function maps the actual keys
that occur to the same space too many times
What does a hash function do - {✔✔Resolution Result Verified Answers
✔✔}-maps a key to an address
In that address, sits a block address that points to a data block
On that data block, we stick that first record which had the key and proceed
If an address is hit again (collision), we can chain
The more data we insert with the same bucket directory size, the longer the list of
blocks will be
Lookup time with static hashing - {✔✔Resolution Result Verified Answers
✔✔}-Costs one block access to get it to memory
Following the pointer, it will take another block access to get to the data
Total = 1-2s
Constant: (1-2) * 0.01s = 0.01 to 0.02s if bucket directory is in main memory
Dynamic hashing expands bucket directory when needed
, Redundancy - {✔✔Resolution Result Verified Answers ✔✔}-Leads to
inconsistency
Database can be useless from the point of view of understanding repetitive fields
Insertion anomaly - {✔✔Resolution Result Verified Answers ✔✔}-occurs
when certain attributes cannot be inserted into the database without the
presence of other attributes, leads to many NULL values or duplicates
Deletion anomaly - {✔✔Resolution Result Verified Answers ✔✔}-deleting
rows may cause a loss of data that would be needed for other future rows
Update anomaly - {✔✔Resolution Result Verified Answers ✔✔}-improper
database organization where a non-primary key item is stored multiple times;
updating the item in one location and not the others causes data inconsistencies
redundant data may not be properly updated
Information loss in normalization - {✔✔Resolution Result Verified Answers
✔✔}-getting more or less information from decomposing a relation into
smaller tables that doesn't reflect reality
Dependency Loss in normalization - {✔✔Resolution Result Verified Answers
✔✔}-If we decompose a table into multiple tables, then we cannot enforce the
functional dependencies, or may lose the ability to enforce them, that are split
between the two relations
Verified Answers Brand New Version Graded
A+
Multilevel index -- B+ tree - {✔✔Resolution Result Verified Answers ✔✔}-
Insertion, deletion, and update operations are implemented to keep the tree
balanced
Only rarely does an overflow at a lower level of the tree propagate more than 1-2
levels up
Static Hashing - {✔✔Resolution Result Verified Answers ✔✔}-You have a
very large space of key values
(for example: Email addresses of regular users)
Hash function h Job of the hash function is to take keys from the key value space
and match them into an address in a bucket directory
Good hash function properties - {✔✔Resolution Result Verified Answers
✔✔}-Distribute values uniformly over the address space
Fill buckets as much as possible because it takes more than just a few blocks, and
therefore needs to be stored somewhere and therefore a piece of it might be
stored on disk and itself be subject to being ported between disk and memory
,Avoid collisions -- Collisions occur when the hash function maps the actual keys
that occur to the same space too many times
What does a hash function do - {✔✔Resolution Result Verified Answers
✔✔}-maps a key to an address
In that address, sits a block address that points to a data block
On that data block, we stick that first record which had the key and proceed
If an address is hit again (collision), we can chain
The more data we insert with the same bucket directory size, the longer the list of
blocks will be
Lookup time with static hashing - {✔✔Resolution Result Verified Answers
✔✔}-Costs one block access to get it to memory
Following the pointer, it will take another block access to get to the data
Total = 1-2s
Constant: (1-2) * 0.01s = 0.01 to 0.02s if bucket directory is in main memory
Dynamic hashing expands bucket directory when needed
, Redundancy - {✔✔Resolution Result Verified Answers ✔✔}-Leads to
inconsistency
Database can be useless from the point of view of understanding repetitive fields
Insertion anomaly - {✔✔Resolution Result Verified Answers ✔✔}-occurs
when certain attributes cannot be inserted into the database without the
presence of other attributes, leads to many NULL values or duplicates
Deletion anomaly - {✔✔Resolution Result Verified Answers ✔✔}-deleting
rows may cause a loss of data that would be needed for other future rows
Update anomaly - {✔✔Resolution Result Verified Answers ✔✔}-improper
database organization where a non-primary key item is stored multiple times;
updating the item in one location and not the others causes data inconsistencies
redundant data may not be properly updated
Information loss in normalization - {✔✔Resolution Result Verified Answers
✔✔}-getting more or less information from decomposing a relation into
smaller tables that doesn't reflect reality
Dependency Loss in normalization - {✔✔Resolution Result Verified Answers
✔✔}-If we decompose a table into multiple tables, then we cannot enforce the
functional dependencies, or may lose the ability to enforce them, that are split
between the two relations
