In databases, transactions are one of the most important concepts for ensuring data correctness, especially when multiple users are working at the same time.

If transactions are not understood properly, it becomes very difficult to understand problems like write conflicts , lost updates , and data inconsistency .

This tutorial explains:

What a transaction is

Why transactions are needed

How write conflicts happen

How databases solve these problems

1. What is a Transaction?

A transaction is a group of SQL operations that are executed as a single unit.

Either everything succeeds, or nothing is applied.

This is called the ACID principle , especially the A (Atomicity) part.

Basic example

BEGIN ;

UPDATE accounts SET balance = balance - 100 WHERE id = 1 ;

UPDATE accounts SET balance = balance + 100 WHERE id = 2 ;

COMMIT ;

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Meaning:

Both updates happen together

If something fails → the database can rollback everything

2.…