Can you explain what is meant by a transaction in the context of SQL and how it functions?

In the context of SQL, a transaction is a sequence of operations on a database that is executed as a single unit. A transaction guarantees that either all operations within it are successfully completed, or none of them affect the database (atomicity).

The main properties of transactions (ACID):

• Atomicity: all operations within a transaction are either fully completed or not executed at all.
• Consistency: after the transaction is completed, the database remains in a correct state.
• Isolation: concurrent transactions do not affect each other.
• Durability: after a transaction is committed, the changes are saved even in case of failures.

Example of using a transaction in SQL:

BEGIN TRANSACTION;
UPDATE accounts SET balance = balance - 100 WHERE id = 1;
UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT;

If an error occurs during the process, you can execute ROLLBACK; — then the changes will be canceled.