Hey, good day everyone and welcome to the third major topic in our database design and management class with this topic focusing on the structured query language or SQL. All right, in our first video for topic number three in our database class, part one, I'm going to provide an introduction to the structured query language. One of the things that I generally think is absent from many technology related curricula is history. I think so these technologies didn't just emerge out of nowhere. They have been developed over long periods of time. They were invented by people and it's good to know where things came from so that we can better understand where we are today and have a better idea about where we're going into the future. Now, the structured query language is most commonly referred to with acronyms, SQL, people will pronounce this as SQL or as SQL, whichever your preference is fine. I'll mix and match a lot of those different things, but it's just a lot easier to say that than structured query language all the time, I'm saying that I have some SQL skills. You can see that this was originally developed by IBM in the 70s and that tells us that it's been around for a long time and there's a reason for that and it's because it is an excellent, easy to use, easy to learn, comprehensive query language that supports relational databases and relational databases have been and continue to be the foundation for almost all modern businesses. That's where we store our data. You can see that the SQL language developed by IBM that later evolved into what we now call the structured query language was designed to support COD's very famous relational model and you can see this was published in CACM, which is a leading computer science journal in 70 and this has become one of the most influential computer science papers ever written. It's been cited just thousands of times, an extraordinarily influential paper that created the entire framework for relational databases, which as I mentioned just a moment ago now serves as the foundation of most modern organizations, this one paper written by Edgar COD has had just an extraordinary influence on the world and I don't want this to seem intimidating. I think what you'll see as we learned this is that it's really not that complicated. It's all quite reasonable and this gives me hope for the future because 1970 is not that long ago. I think that you'll find as you learn this that it's pretty amazing that it took humans all the way up until 1970 to figure this out. That's a pretty simple idea. The whole notion of relational model for storing data is quite simple. So this gives me hope because it means that there are probably lots of really excellent ideas out there that are simple that even today haven't yet been discovered. We just haven't for whatever reason, haven't come across it yet even if it's simple and powerful idea. Who knows, let that motivate you. Now, in the structural query language is based on is largely based on relational algebra. However, we're not going to take an algebraic approach to it. Nevertheless, I will point out a few types of algebra related concepts, I should say relational algebra concepts, so things that you probably remember from about 7th or 8th grade, like Venn diagrams, right? Where you have things that look like this and you look for what's going on here and you can say, okay, here's the intersection of these three circles and then you have other things like, oh, I don't know, here's the union of these things. We can think about what's happening in our structured query language statements in the form of relational and once we get to joins in particular, I'll use some of these concepts to help you just conceptualize or visualize what's happening as we write these SQL statements. But if you're fairly familiar with remember these sorts of Venn diagrams that are part of relational algebra, then you should have no problem understanding the idea of joining tables together and different types of joins. We'll talk about inner joins and outer joins and stuff like that. That can be on our list of things to look now finally, I want to mention that today the structured query language is a standard, right? It's both standard in the American National Standards Institute and the International Standards Organization. This is a standardized data language. It is therefore built in and supported by every major enterprise level relational database vendor. And this is one of the reasons why you know, learning the structured query language is so valuable. It is universally implemented in these relational databases, enterprise level relational databases. So that means if you can learn this, you only have to learn it once and you will be able to sit down and use any enterprise level relational database with very little learning curve. And if you can learn to write SQL statements, you can write statements for Microsoft SQL Server or Oracle or IBM DB2 or MySQL or Postgres SQL, once you learn it, you can work with any sort of database. So the technology, the specific technology becomes less important. It's more that if you could just learn this language, hey, you can use any of them. So whatever companies you go to work for, they're going to have some sort of database and it won't really matter because the actual database that they've chosen can be used with your SQL or SQL statements. So this is not a programming language. Many people are intimidated. They think that structured query language is a programming language and programming languages are hard to learn. But that's not true in this case. It's not a programming language. As it says here, it's a data sub language. And it's much simpler and much easier to learn than any sort of programming language that's out there. SQL was designed from the very beginning to be easy to learn, easy to understand. It uses just a very small set of common English language keywords. And once we learn those words and we learn the patterns, that is the way that we arrange them in order to try to accomplish what it is we're trying to accomplish, then writing SQL statements becomes very straightforward. There's much less variety in the types of SQL statements that you can write than there is, say with what you can write with a programming language. And very few keywords comparatively speaking, if you want to learn a programming language like C plus loss, there'll be more than 100 keywords in there. And SQL is nothing like that. It maybe has, I don't know, 15 or 20. So it's not a big deal at all. And again, they're very common, simple English language words. Hopefully it'll be pretty easy for us to start to learn and internalize SQL as a new skill. Now, the structured query language can be understood as consisting of three different parts. So if we want to think of, I don't know, like a pie chart, here's the structured query language. And we can divide that up into some wedges here. And in that way, we can understand it. So we have this sort of three-part structure to the structured query language. And these parts, respectively, are the DDL. This is the data definition language. And this contains the set of SQL commands that we use to define the structure of our database. So things like tables, relationships, attributes, data types, constraints, these kinds of things are all part of the DDL. Okay. The second part is called the DML or data manipulation language. And this is the part of the structured query language that allows us to actually work with data. So if we want to do any of the four basic data operations, create new data, read existing data, update existing data or delete data, we do those with the DDL part of the broader structured query language. Those are part of the DML or data manipulation language component. And finally, we have the DCL. And we're not going to learn about DCL much at this point in our class, but we will revisit this once we get to our sixth topic when we learn about database security model and how we can go about doing things like creating user accounts, creating roles, assigning, granting, and revoking permissions, these types of things. That's done as part of the DCL. And so as you can see here on this slide, the DCL is used for handling things like permissions, user accounts, and roles, and so on. So we'll revisit that a little later in our class. But as for for today, our focus is going to be primarily on DDL. And then starting next time, we'll get into DML. So just think of the structured query language as consisting of these three parts. One is related to the structure of the database. The other is related to the data themselves. And the third is related to control things like user accounts, permission, those sorts of things.