Explanation: A deadlock is a situation where two or more transactions are waiting for each other to release locks, causing a standstill.

Explanation: ACID stands for Atomicity, Consistency, Isolation, and Durability, which are key properties of database transactions.

Explanation: Atomicity ensures that a transaction is treated as a single, indivisible unit of work, and it is either fully completed or fully rolled back in case of failure.

Explanation: Atomicity ensures that a transaction is either fully completed or fully rolled back in case of failure, maintaining data integrity.

Explanation: Durability ensures that a transaction, once committed, cannot be undone or rolled back, and its changes are permanent.

Explanation: Durability ensures that once a transaction is committed, it is not lost even in the event of a system crash or failure.

Explanation: Durability ensures that transactions are executed in a specific order, as they are received by the database, to maintain data integrity.

Explanation: Consistency ensures that a transaction brings the database from one consistent state to another, maintaining data integrity.

Explanation: Isolation ensures that concurrent transactions do not interfere with each other and appear to be executed serially, preventing data inconsistencies.

Explanation: Durability ensures that once a transaction is committed, its changes are permanent and survive system failures.

Explanation: The "ROLLBACK" statement in database transactions is used to undo a transaction and revert any changes made during the transaction.

Explanation: The "ROLLBACK TO SAVEPOINT" statement in database transactions is used to roll back a transaction to a specific savepoint within the transaction, allowing for partial rollbacks.

Explanation: The "SAVEPOINT" statement in database transactions is used to create a point within a transaction to which you can later roll back, allowing for partial rollbacks.

Explanation: The "COMMIT" statement in database transactions is used to commit a transaction and make its changes permanent in the database.

Explanation: A non-repeatable read occurs when a transaction reads data that has been updated by another transaction before the first transaction is completed, leading to inconsistent results.

Explanation: A phantom read occurs when a transaction reads data that has been deleted by another transaction before the first transaction is completed, leading to unexpected results.

Explanation: A "dirty read" occurs when a transaction reads data that has not been committed by another transaction, potentially leading to inconsistent results.

Explanation: In many relational databases, the SQL statements "BEGIN" or "START TRANSACTION" are used to explicitly start a transaction.

Explanation: The "ROLLBACK" statement in many relational databases is used to explicitly roll back a transaction, undoing its changes.

Explanation: In the context of database transactions, "commit" refers to making the transaction's changes permanent in the database.

Explanation: The Read Committed isolation level ensures that a transaction can read only committed data, preventing dirty reads.

Explanation: The Repeatable Read isolation level allows for repeatable reads, preventing dirty reads and non-repeatable reads.

Explanation: The Read Uncommitted isolation level allows a transaction to read uncommitted data from other transactions, offering the lowest level of isolation.

Explanation: The Serializable isolation level provides the highest degree of isolation, preventing dirty reads, non-repeatable reads, and phantom reads, but it may lead to more contention.

Explanation: The Serializable isolation level provides the highest level of data consistency but may lead to more contention and potential performance issues due to locking.