Before we get to the examples, we will cover those topics briefly. To understand the examples in this post, you will first need to understand what a transaction is and some things about isolation levels. As you see them “in action,” you will understand what each one accomplishes and when to use each.
This blog post will help you experience all six isolation levels. SQL Server prevents problems that can arise from concurrency situations, such as the above in which concurrent attempts to access and/or modify the same data are made, by implementing six isolation levels.
Were it not for isolation levels, trouble would be brewing on the horizon… You are going to transfer $400 out of an account that has a $500 balance, and your family member is about to withdraw $300 from that same account. Just as you are punching in your secret code, so is a family member punching in their secret code at an ATM across town.
