cse 180 midterm study set UPDATED
ACTUAL Exam Questions and CORRECT
Answers
What is a database? - CORRECT ANSWER - a collection of data (describes the activities
of one or more related organizations over time)
What is a Database Management System? - CORRECT ANSWER - a software system
designed to assist in creating, storing, accessing, and updating a database
What are the key characteristics of a DBMS? - CORRECT ANSWER - 1. Data Model
(abstraction of the underlying data)
2. High-level language for manipulating data (defining, updating, retrieving and processing data)
3. Transaction Processing (concurrent access and updates, crash recovery)
4. Access control (limit access of certain data to certain users)
What are the advantages of a DBMS? - CORRECT ANSWER - - users only need to
understand the data model and high-level language for manipulating data
- illusion that they are the only users of the DBMS
- data integrity is not compromised by system failures
- queries are automatically optimized for efficiency
- integrity of data is automatically enforced
- many different applications use data
- well-understood database administration capabilities.
What are the ACID properties? - CORRECT ANSWER - 1. Atomicity
2. Consistency
3. Isolation
4. Durability
, What is Atomicity? - CORRECT ANSWER - Atomicity guarantees that either all the
operations in the group are executed to completion or non of the operations are executed.
All-or-nothing, no in-between.
Ex: money is deducted from a source and if any anomaly occurs, the changes are discarded and
the transaction fails.
What is Consistency? - CORRECT ANSWER - Consistency guarantees that changes
made within a transaction are consistent with database constraints.
Ex: there is a constraint that the balance should be a positive integer. If we try to overdraw
money, then the balance won't meet the constraint therefore leading to failure of the transaction.
What is Isolation? - CORRECT ANSWER - Isolation ensures that all transactions run in
an isolated environment. (critical section) That enables running transactions concurrently
because transactions don't interfere with each other.
Ex: Our account balance is $200. Two transactions for a $100 withdrawal start at the same time.
The transactions run in isolation which guarantees that when they both complete, we'll have a
balance of $0 instead of $100.
What is Durability? - CORRECT ANSWER - Durability means that changes made by
committed transactions don't go away, even if there are failures (e.g. of applications, processors,
memories or storage), they persist.
Ex: consider a power failure immediately after a database has confirmed that money has been
transferred from one bank account to another. The database should still hold the updated
information even though there was an unexpected failure.
ACTUAL Exam Questions and CORRECT
Answers
What is a database? - CORRECT ANSWER - a collection of data (describes the activities
of one or more related organizations over time)
What is a Database Management System? - CORRECT ANSWER - a software system
designed to assist in creating, storing, accessing, and updating a database
What are the key characteristics of a DBMS? - CORRECT ANSWER - 1. Data Model
(abstraction of the underlying data)
2. High-level language for manipulating data (defining, updating, retrieving and processing data)
3. Transaction Processing (concurrent access and updates, crash recovery)
4. Access control (limit access of certain data to certain users)
What are the advantages of a DBMS? - CORRECT ANSWER - - users only need to
understand the data model and high-level language for manipulating data
- illusion that they are the only users of the DBMS
- data integrity is not compromised by system failures
- queries are automatically optimized for efficiency
- integrity of data is automatically enforced
- many different applications use data
- well-understood database administration capabilities.
What are the ACID properties? - CORRECT ANSWER - 1. Atomicity
2. Consistency
3. Isolation
4. Durability
, What is Atomicity? - CORRECT ANSWER - Atomicity guarantees that either all the
operations in the group are executed to completion or non of the operations are executed.
All-or-nothing, no in-between.
Ex: money is deducted from a source and if any anomaly occurs, the changes are discarded and
the transaction fails.
What is Consistency? - CORRECT ANSWER - Consistency guarantees that changes
made within a transaction are consistent with database constraints.
Ex: there is a constraint that the balance should be a positive integer. If we try to overdraw
money, then the balance won't meet the constraint therefore leading to failure of the transaction.
What is Isolation? - CORRECT ANSWER - Isolation ensures that all transactions run in
an isolated environment. (critical section) That enables running transactions concurrently
because transactions don't interfere with each other.
Ex: Our account balance is $200. Two transactions for a $100 withdrawal start at the same time.
The transactions run in isolation which guarantees that when they both complete, we'll have a
balance of $0 instead of $100.
What is Durability? - CORRECT ANSWER - Durability means that changes made by
committed transactions don't go away, even if there are failures (e.g. of applications, processors,
memories or storage), they persist.
Ex: consider a power failure immediately after a database has confirmed that money has been
transferred from one bank account to another. The database should still hold the updated
information even though there was an unexpected failure.
