‫Acid, which stands for a tomasetti, consistency, isolation and durability, are four critical properties
‫of relational database systems.
‫I think any engineer working with the relational databases such as Postgres, MySchool, SQL Server,
‫Oracle and even no sequel databases or graph databases must really understand these four building blocks
‫and fundamentals and first principles that build database systems.
‫In this course, we'll go through these four properties in details, and I'll explain why each of these
‫properties is critical to build and use relational databases successfully.
‫Let's get started.
‫So part of the work that we're going to discuss in this section is what is a transaction before we even
‫start talking about these four properties?
‫We need to understand what is a database transaction at its core.
‫And once we understand this, then we're going to jump into the first property at Thomas City.
‫What is it exactly?
‫Why is it the most important thing to guarantee consistency?
‫Speaking of consistency, we really need to talk about the transaction isolation as I start multiple
‫transactions concurrently.
‫All of these are accessing my data.
‫All of these transaction, at the same time changing my data.
‫What does it mean to a for these transactions to be isolated from each other?
‫What can they see?
‫What can not what should not they see all these results in to the consistency?
‫Fourth parameter, I flipped the order here because I really believe talking about automaticity and
‫isolation before consistency is actually critical to understand consistency.
‫Because now, if you have a transaction and this transaction change is something that I just wrote,
‫then you are going to get the result.
‫That is unexpected, that affects your consistency.
‫You get a data that you didn't expected.
‫It's bizarre, right?
‫And finally, the most important one, one of the most actually and one of the properties that a lot
‫of NoSQL databases play with durability.
‫The some databases sacrifice durability for performance, and nothing wrong with that is just understanding
‫the concept of durability that when I actually commit that transaction, when I actually say save,
‫this should really be persisted in an non-volatile place so that I can go back and read this data.
‫Even if my databases crash, even if I lost power, I can still get access to my data.
‫We're going to talk about all of these in detail if you are interested in this thing.
‫Stay tuned and see you in their next lecture.
‫Oh, I forgot to mention one thing.
‫By the end of this section, I added a little bit of a small quiz that I think you guys were going to
‫enjoy.
‫And obviously, the answers are in the quiz.
‫And even if you pick any wrong answer, I give you detailed explanation why that answer is not the actual
‫correct answer, right?
‫And we have all sorts of great discussions in this course as well.
‫Now let's jump to the next lecture.