Microsoft® SQL Server 2012 Unleashed

What Is a Transaction?

A transaction is one or more SQL statements that must be completed as a whole or, in other words, as a single logical unit of work. Transactions provide a way of collecting and associating multiple actions into a single all-or-nothing multiple-operation action. All operations within the transaction must be fully completed or not performed at all.

Consider a bank transaction in which you move $1,000 from your checking account to your savings account. This transaction is, in fact, two operations: a decrement of your checking account and an increment of your savings account. Consider the impact on your finances if the bank’s server went down after it completed the first step and never got to the second! When the two operations ...