What are ACID properties in databases?

ACID properties in databases refer to Atomicity, Consistency, Isolation, and Durability, which ensure reliable processing of transactions.

ACID is an acronym that stands for Atomicity, Consistency, Isolation, and Durability. These are a set of properties that guarantee that database transactions are processed reliably. They are fundamental principles for any system that wants to ensure data integrity and consistency, even in the event of errors, power failures, and other mishaps.

Atomicity ensures that a transaction is treated as a single, indivisible unit of work. This means that either all the changes made in a transaction are committed to the database, or if the transaction fails, none of the changes are committed. For example, if you are transferring money from one bank account to another, atomicity ensures that the money is either deducted from one account and added to the other, or if something goes wrong, no changes are made at all.

Consistency ensures that a transaction brings the database from one valid state to another. The database has a set of rules defined, known as integrity constraints, and consistency ensures that these rules are not violated. For instance, in a school database, a student cannot be enrolled in a class that doesn't exist.

Isolation ensures that concurrent execution of transactions leaves the database in the same state as if the transactions were executed sequentially. This means that the execution of one transaction is not affected by another. For example, if two people are booking a seat on a flight at the same time, isolation ensures that they can't book the same seat.

Durability guarantees that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors. This means that once the database tells the user that a transaction has succeeded, the user can be sure that the transaction has been recorded and will not be undone. For example, once you receive a confirmation that your online order has been placed, you can be sure that the order will not be lost due to a system failure.

In summary, ACID properties are crucial for maintaining the integrity and reliability of data in a database. They ensure that transactions are processed completely and correctly, and that data remains consistent and accurate, even in the face of potential disruptions.