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All right.

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So we're going to start off by taking a bit of a step back and talking about two very high level general

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questions that are pretty central to everything this course is about.

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And they are.

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First off, what is database?

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It seems like a pretty straightforward question, but there is a little bit of terminology we need to

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discuss.

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And then secondly, why do they matter?

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So let's start off with the first one.

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What is a database?

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What actually makes something database?

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And there are a couple of definitions that we could go with here.

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I kind of synthesized some of them into my own definition.

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That has two parts.

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And the first part is that it's a collection of data, which seems pretty straightforward.

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There are all sorts of collections of data around us in the real world, things like when you go to

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your doctor's office and there's a filing cabinet full of medical records, or even just a to do list

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or a list of things to buy at the grocery store that qualifies as a collection of data.

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Or going back a little bit in time, if you remember what Rolodexes were, a Rolodex full of different

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people's contact information that qualifies as a database under this definition.

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Speaking of archaic technology like a Rolodex, another example of a database is a phone book.

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So I say this mainly jokingly, but I actually have some siblings who don't know what phone book is,

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or they've never seen one or used one before.

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It's a gigantic book, basically, that lets you look up people's phone numbers based off of their name.

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So it's usually organized by last name alphabetically for people.

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So you would flip through the book until you find someone's last name, and then you would try and match

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the first name and then you find their phone number.

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So let's take a quick example here.

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This is a fictional phone book.

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Think of it as just a little section of a phone book that has tens of thousands of entries.

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And these are fictional characters alphabetically organized by their last name.

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So Archie Andrews becomes before Betty Cooper, who comes before Ned Flanders and so on.

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And then we have corresponding phone numbers.

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So imagine you have a gigantic phone book with this information in it, and I ask you to do something

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like find Ned Flanders phone number.

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Well, it's actually pretty straightforward.

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As long as you're comfortable using the alphabet in alphabetical order.

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You flip through the book until you find F, F, L, and so on, until you find Ned Flanders.

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And then you find his phone number.

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It's what the phone book is made for.

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However, it gets a little trickier or a lot trickier, really.

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If I asked you to do something like find everyone in the phone book who has the first name Ned.

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There isn't an easy way to do this.

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You basically would have to go through every entry in the book and check for however many thousands

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there are.

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Is this person's name Ned?

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So I have a couple other questions that are similarly difficult.

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So the point here is just if you were to find all phone numbers with a particular area code or to find

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all people who have a three letter first name, it's not easy.

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And it would take a lot of time, like a ton of time.

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So that brings me to the next component of the definition of what makes something a database, in my

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opinion, which is not just a collection of data, it also contains a method for accessing and manipulating

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that data.

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So going back to this phone book, we would want a way, some sort of program or code that would allow

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us to do things like find everybody with the first name Ned or find all people who have a three letter

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first name, or even do things like add a new person into the phonebook or change area codes or change

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phone numbers, or get crazy and just delete people from our phonebook or delete everybody.

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If we wanted to, we would have some sort of program or code as part of our database that would help

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with that, that would allow us to interface with the data.

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So I did say we were going to dive a little bit into jargon and terminology.

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I usually try and stay away from that early on while I try and stay away from that in general, but

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especially early on in the course.

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Basically, if you've read about databases, if you've used one before, if you've read a blog post

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about them, you may have come across the term database management system or relational database management

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system or DMS or RB DMS and all these different acronyms.

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Basically, this right here, what I have on the screen database versus database management system refers

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to the fact that what I just talked about, having data, a collection of data and then having an interface

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for that data are two different things.

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So let me show you a quick example.

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Imagine that you have an application, let's say it is a dating app, and then you have a database and

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you're storing all sorts of information, all the different users, all the different messages that

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have been sent, the photos, whatever else goes into your dating app.

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But on its own, the database here is basically like our phonebook.

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It's a gigantic collection of data, which is great for storing data, but it really doesn't let us

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do very much.

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You can almost think of it as if it was a gigantic file on your computer.

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So for our application to be able to do things like update somebody's username in the database or edit

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their profile photo or delete a user if they want to leave our application, whatever it is, there's

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a database management system that allows us to interface with that database.

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So it's just the code or the program that does the talking to our database for us.

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So we talk to our database management system and it talks to the database.

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Okay.

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So for the most part, we're out of the weeds with the jargon here.

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The reason I brought this up, though, is that oftentimes when people talk about a database, you actually

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hear them referring to both of these things, the database management system and the database together

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just as a database.

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So what I have right here is a list of some of the more common databases you'll run into.

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And actually, I just did it there.

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What I was just talking about these four things, PostgreSQL, my SQL, Oracle SQL Light, they're not

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technically databases, they're actually database management systems, but for the most part, people

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just call them databases.

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So when we say things like, my SQL is one of the most commonly used databases, it's actually one of

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the most commonly used database management systems.

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So it's not the end of the world if you forget about that.

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But it is important because it will help you understand later on when we actually start talking about

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SQL, when we start talking about some of the code that you write to interact with the database, I

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think it will help you understand what you're doing and that you're giving commands to this database

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management system, which then goes and gives commands to the actual data itself or to the database

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itself.

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So to wrap everything up, here's a little bit of a synthesized definition.

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What is the database?

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Well, it's a structured set of computerized data with an accessible interface.