What is the difference between 'dirty read' and 'non-repeatable read' in the context of transaction isolation levels?
- Dirty read: Reading committed data
- Dirty read: Reading uncommitted data
- Non-repeatable read: Reading committed data
- Non-repeatable read: Reading uncommitted data
In the context of transaction isolation levels, a 'dirty read' occurs when a transaction reads uncommitted data from another transaction, while a 'non-repeatable read' happens when a transaction reads data committed by another transaction but the data changes before the first transaction completes. Understanding these concepts is crucial in managing data consistency and isolation in concurrent transactions.
The isolation level that allows neither dirty reads nor non-repeatable reads is called _________.
- Read Committed
- Read Uncommitted
- Repeatable Read
- Serializable
The Serializable isolation level ensures neither dirty reads nor non-repeatable reads, providing the highest level of isolation.
The concept of ________ allows multiple users to make changes to the database without affecting each other.
- Concurrency Control
- Consistency Management
- Isolation
- Transaction Control
The concept of Concurrency Control allows multiple users to make changes to the database concurrently without affecting each other, ensuring data integrity and consistency.
In a distributed system, when two databases must be updated as part of a single transaction, which transaction management technique is most appropriate?
- Isolation (I)
- Optimistic Concurrency Control (OCC)
- Pessimistic Concurrency Control (PCC)
- Two-Phase Commit (2PC)
The Two-Phase Commit (2PC) is most appropriate for managing transactions in a distributed system involving updates to multiple databases, ensuring atomicity and consistency across the distributed environment.
Which Java statement is used for handling SQL exceptions?
- finally
- if-else
- switch
- try-catch
The try-catch statement is used for handling SQL exceptions in Java. It allows you to catch and handle specific exceptions that may occur during the execution of the code.
What is the main purpose of using try-catch blocks in database operations?
- To close connections
- To create databases
- To execute SQL queries
- To handle exceptions
The main purpose of using try-catch blocks in database operations is to handle exceptions that may occur during the execution of SQL queries or other database-related operations.
Which method is used to retrieve detailed information about an SQL exception?
- getErrorCode()
- getMessage()
- getSQLException()
- getSQLState()
The getErrorCode() method is used to retrieve the specific error code associated with an SQL exception, providing detailed information about the exception.
How can you handle a situation where a database connection is lost during a transaction?
- Commit the transaction
- Ignore the issue and proceed
- Retry the transaction
- Rollback the transaction
If a database connection is lost during a transaction, you can handle it by retrying the transaction, allowing for the re-establishment of the connection and completion of the operation.
What is the significance of the finally block in JDBC operations?
- To handle exceptions
- To improve performance
- To optimize code execution
- To release resources
The finally block in JDBC operations is significant for releasing resources, ensuring that resources like database connections are properly closed, regardless of whether an exception occurs.
How do you differentiate between checked and unchecked SQL exceptions?
- Checked exceptions are SQLExceptions
- Checked exceptions are caught at compile-time
- Unchecked exceptions are SQLExceptions
- Unchecked exceptions are caught at compile-time
Checked SQL exceptions are those derived from SQLException, and they must be either caught or declared to be thrown. Unchecked SQL exceptions are those that extend RuntimeException.