DataBase Transactions

A database transaction has a very specific meaning beyond regular English transaction. It refers to a set of steps that are done together (usually in sequence, but not necessarily so). Together, these steps are a transaction, and what's important is that the transaction as a whole either succeeds or fails. If any of the steps fails, the entire transaction fails. As a result of transaction failure, the database is said to be rolled back to its condition before the transaction began.

When a database supports transactions, the failure of any part of a transaction means the entire transaction fails and the database is set to whatever it was before the transaction started. All of this happens in an ACID-compliant database.

In in many other implementations of SQL (such as SQLite), a transaction consists of a number of SQL statements bracketed by

BEGIN TRANSACTION

and

END TRANSACTION