What Are SQL Transactions and ACID, How Do They Work?

The most fundamental way to ensure data integrity in database management is to manage transactions (transaction) correctly. SQL transactions and the concept of ACID ensure that changes made in the database are completed smoothly, reliably, and consistently. So, how do SQL transactions work and what is the importance of ACID properties? In this article, we will examine these important concepts in detail both theoretically and practically.

What is an SQL Transaction?

An SQL transaction is a set of operations in which one or more SQL queries must be successfully completed as a whole. All queries within the transaction must succeed; if any of them fail, all operations performed are rolled back. In this way, no inconsistent or erroneous data is formed in the database.

A Simple Example of an SQL Transaction

BEGIN TRANSACTION;
UPDATE accounts SET balance = balance - 500 WHERE account_no = 1001;
UPDATE accounts SET balance = balance + 500 WHERE account_no = 1002;
COMMIT;

In the example above, money transfer is performed between two different accounts. If an error occurs during the transfer, the transaction is automatically rolled back and both tables revert to their original state before the operation. In this way, SQL transactions ensure the integrity of the operation.

What is the Concept of ACID?

To ensure the reliability of SQL transactions, four basic principles called ACID (Atomicity, Consistency, Isolation, Durability) are used. These concepts guarantee the safety and stability of database operations.

ACID Properties in Detail

• Atomicity: All steps in the transaction are either fully executed or not executed at all.
• Consistency: Data integrity is maintained before and after the operation.
• Isolation: Transactions running at the same time proceed without affecting each other.
• Durability: If the transaction is successful, the changes made become permanent; even if the system crashes, the data is preserved.

ACID's Contribution to SQL Transactions

For example, in a banking application, when transferring money, the balance should be deducted from the sender's account and added to the recipient's account. If the transaction is interrupted, ACID principles come into play to prevent faulty money transfers.

Conclusion

SQL transactions and the ACID concept are the two indispensable main pillars of modern database applications. These two structures work together to ensure consistent, reliable, and isolated operations. Every software developer should understand the logic of SQL transactions and the advantages provided by ACID. In this way, data loss and inconsistencies due to the database can be prevented.