1 00:00:00,290 --> 00:00:01,480 All right we'll come back. 2 00:00:01,530 --> 00:00:04,630 It's time for us to start working with databases interact locations. 3 00:00:04,770 --> 00:00:09,270 And before we actually write code I just want to take a few minutes here so we'll be pretty quick to 4 00:00:09,270 --> 00:00:14,850 talk about what databases actually are and then to introduce two broad categories of databases which 5 00:00:14,850 --> 00:00:18,690 are sequel databases or Escudo versus no sequel or no. 6 00:00:18,690 --> 00:00:20,120 Q All databases. 7 00:00:20,720 --> 00:00:21,060 OK. 8 00:00:21,060 --> 00:00:26,160 So let's begin here and to start I want to illustrate the problem that we have right now. 9 00:00:26,250 --> 00:00:32,340 I have the POST request demo running this friends up where I can list all my friends and we can add 10 00:00:32,340 --> 00:00:33,410 some new friends. 11 00:00:33,600 --> 00:00:39,450 I just made a new one today named Garfield and another friend named her mine. 12 00:00:40,550 --> 00:00:41,120 OK. 13 00:00:41,310 --> 00:00:48,780 And then I can go back here and if I shut off the server and started again and I refresh my page. 14 00:00:49,340 --> 00:00:51,520 Gosh you just lost two friends. 15 00:00:51,570 --> 00:00:57,240 So the problem that we're facing is that our data doesn't persist if our server stops for any reason 16 00:00:57,690 --> 00:00:59,430 whether it's because we turned it off. 17 00:00:59,430 --> 00:01:00,390 We wanted to restart it. 18 00:01:00,390 --> 00:01:06,360 We made some changes to the code or if it's because the power goes out or some freak event happens if 19 00:01:06,360 --> 00:01:12,990 the server stops we would lose all data which is obviously a really really bad thing for a web application 20 00:01:13,010 --> 00:01:13,320 . 21 00:01:13,600 --> 00:01:18,450 If Facebook lost your data every time you logged out or every time the server stopped that would be 22 00:01:18,450 --> 00:01:21,700 really really bad for Facebook although it might be pretty good for me. 23 00:01:21,840 --> 00:01:22,980 I'd be productive. 24 00:01:23,040 --> 00:01:27,840 I stopped comparing myself to my friends at Stop trying to prove to everyone that I live a fun life 25 00:01:28,050 --> 00:01:29,530 and I just get stuff done. 26 00:01:29,940 --> 00:01:33,940 So all of this is to say that databases will help us with this problem. 27 00:01:34,230 --> 00:01:38,950 So let's talk about what databases are in the simplest possible definition. 28 00:01:38,950 --> 00:01:47,160 The database is a collection of information data but a database isn't just a collection of information 29 00:01:47,160 --> 00:01:47,480 . 30 00:01:47,490 --> 00:01:53,910 So if we had a file just a text file and sublime that had a bunch of information and saved it that wouldn't 31 00:01:53,910 --> 00:01:55,100 be a database. 32 00:01:55,380 --> 00:01:57,100 Yes it might store data for us. 33 00:01:57,120 --> 00:02:02,100 It might be a collection of information but the other important aspect of databases is that they have 34 00:02:02,100 --> 00:02:08,130 an interface for interacting with that data whether it's adding new information like adding a new user 35 00:02:08,130 --> 00:02:14,550 to the database or if it's removing all users or editing an existing user or whatever it is there needs 36 00:02:14,550 --> 00:02:16,830 to be a way for us to interact with the data. 37 00:02:16,890 --> 00:02:22,740 So a database is a collection of information slushed data and it has an interface. 38 00:02:23,160 --> 00:02:27,350 When I say interface I mean that we can write code to interact with it. 39 00:02:27,360 --> 00:02:33,470 So if you've ever worked with a sequel database before you might have seen things like this select star 40 00:02:34,090 --> 00:02:36,340 I should capitalize this. 41 00:02:37,820 --> 00:02:41,270 It's like star from users. 42 00:02:41,280 --> 00:02:44,630 Or you might see something like insert blah blah blah into. 43 00:02:44,730 --> 00:02:51,930 And this is a language called sequel and this is the interface to some databases the language that we'll 44 00:02:51,930 --> 00:02:53,730 be using looks like this. 45 00:02:53,910 --> 00:03:08,820 D-B dot dogs dot find or D-B dot dogs dot delete and will delete the dogs where we have age just 14 46 00:03:08,830 --> 00:03:08,950 . 47 00:03:09,060 --> 00:03:13,430 Unfortunately all my dogs have died at that age and I want to talk about it and I'll delete all dogs 48 00:03:13,430 --> 00:03:14,790 where age is 14. 49 00:03:15,210 --> 00:03:20,070 We'll get into the specifics of the language in the next video but I just want you to be aware. 50 00:03:20,160 --> 00:03:24,690 This is what I mean when I say that there's an interface to the collection of data slash information 51 00:03:24,700 --> 00:03:25,270 . 52 00:03:25,830 --> 00:03:26,400 OK. 53 00:03:26,400 --> 00:03:31,950 So the last thing I want to do is talk about the two broad categories or two of the broad categories 54 00:03:31,950 --> 00:03:38,240 of databases and those are sequel which is also called relational databases versus no. 55 00:03:38,250 --> 00:03:43,830 As you well know sequel which are called non-relational databases when I'm talking to my students about 56 00:03:43,830 --> 00:03:49,830 databases a lot of them have had some experience with some sort of database whether they were in marketing 57 00:03:49,830 --> 00:03:52,130 or retail or something online. 58 00:03:52,200 --> 00:03:57,810 Pretty much every company out there has some database usually lots of databases with lots of information 59 00:03:57,810 --> 00:04:05,010 in it whether it's a database for all of the Skewes in the gap or a database for payroll of all the 60 00:04:05,010 --> 00:04:09,870 employees and what they've been paid and when or if it's a bunch of data on users like Facebook has 61 00:04:10,140 --> 00:04:14,700 where it's storing all of your user information on your photos your comments your posts your likes your 62 00:04:14,700 --> 00:04:17,420 tags all that stuff is stored in databases. 63 00:04:17,430 --> 00:04:22,470 When I talk to students about databases the students who are familiar and have experience with databases 64 00:04:22,830 --> 00:04:30,120 almost always only have experience with sequel or relational databases and that's because sequel databases 65 00:04:30,180 --> 00:04:34,950 have been around the longest and they're what most people think of when they think of a database. 66 00:04:35,280 --> 00:04:38,970 So now let's talk about what sequel data bases what relational means. 67 00:04:39,270 --> 00:04:43,740 So sequel databases are tabular databases and they're flat. 68 00:04:43,830 --> 00:04:45,120 Let me show you what I mean. 69 00:04:45,120 --> 00:04:52,290 So I have some crude diagrams that I typed up and this is showing what the tables for a database involving 70 00:04:52,290 --> 00:04:54,530 users and comments could look like. 71 00:04:54,540 --> 00:04:57,760 Let's just start by focusing on the users. 72 00:04:57,840 --> 00:05:04,110 So what we have to do in a relational database or Seacole database is we define what a user looks like 73 00:05:04,120 --> 00:05:04,320 . 74 00:05:04,500 --> 00:05:12,840 So one user has an ID as a name and age and a city and then every single user that we add must follow 75 00:05:12,840 --> 00:05:13,520 that pattern. 76 00:05:14,420 --> 00:05:20,280 So we're defining these tables and then we're adding instances of the user or of users to this table 77 00:05:20,840 --> 00:05:23,780 and then let's suppose I also have comments. 78 00:05:23,840 --> 00:05:26,220 So I want a user to be able to comment. 79 00:05:26,330 --> 00:05:33,830 So I have a comments table and all that a comment has is an ID and some text of the comment like EHLO 80 00:05:33,830 --> 00:05:41,030 or come visit Montana or I love puppies if I want there to be a relationship between users and comments 81 00:05:41,600 --> 00:05:45,130 where a user can have a comment those associated with it. 82 00:05:45,320 --> 00:05:51,370 So Ira I hear who's 24 from Missoula can be associated with some of these comments here. 83 00:05:51,410 --> 00:05:55,160 Like come visit Montana and seriously Montana is great. 84 00:05:55,160 --> 00:06:00,590 The only way to do that to express this relationship is through another table which is what we have 85 00:06:00,590 --> 00:06:01,120 here. 86 00:06:01,330 --> 00:06:03,020 And these are called join tables. 87 00:06:03,170 --> 00:06:08,450 And what this table does is it joins a user's ID with a comment Id. 88 00:06:08,450 --> 00:06:14,700 So in this case we see that the user with ID one owns the comment with ID 3. 89 00:06:14,930 --> 00:06:24,560 So that means that Tim said that I love puppies and the user with the idea of two commented twice and 90 00:06:24,560 --> 00:06:27,270 those comments or idea of to an idea for. 91 00:06:27,560 --> 00:06:33,080 So we can see that IRA commented come visit Montana and also seriously. 92 00:06:33,080 --> 00:06:34,360 Montana is great. 93 00:06:34,370 --> 00:06:36,470 And yes 110 is great. 94 00:06:36,500 --> 00:06:39,740 What I really want to show with all of this is that everything is tabular. 95 00:06:39,800 --> 00:06:44,020 So we have to define a table ahead of time and its not very flexible at all. 96 00:06:44,120 --> 00:06:48,830 Lets suppose I wanted to add another attribute to IRA that was favorite color and I wanted to set it 97 00:06:48,830 --> 00:06:50,590 to be purple. 98 00:06:50,690 --> 00:06:54,240 I would then have to go an add favorite color for everyone. 99 00:06:54,240 --> 00:07:01,040 Let's just call it a fav color and it would have to be empty so I'd have to have Noel or undefined or 100 00:07:01,040 --> 00:07:05,900 nyl or just false or something here for every single person. 101 00:07:06,020 --> 00:07:07,450 So it's not flexible. 102 00:07:07,530 --> 00:07:13,010 What I have to do is define exact patterns of what a user looks like and then I need to follow that 103 00:07:13,010 --> 00:07:15,300 pattern very closely. 104 00:07:15,410 --> 00:07:22,760 So the other type of database non-relational databases or no as well databases and you probably catch 105 00:07:22,760 --> 00:07:23,900 them going here. 106 00:07:23,900 --> 00:07:26,240 We don't have to define patterns ahead of time. 107 00:07:26,240 --> 00:07:27,660 They're much more flexible. 108 00:07:27,890 --> 00:07:32,400 So here's an example of representing irah using a non-relational database. 109 00:07:32,480 --> 00:07:33,670 There are no tables. 110 00:07:33,710 --> 00:07:37,880 So we don't have to define this tabular structure and things can be nested. 111 00:07:37,880 --> 00:07:40,380 So it's not a flat database. 112 00:07:40,670 --> 00:07:43,780 So you can see here it looks just like javascript. 113 00:07:43,790 --> 00:07:45,360 In fact it's really really similar. 114 00:07:45,530 --> 00:07:51,590 It's something called beats on which stands for binary javascript object notation but it's basically 115 00:07:51,680 --> 00:07:57,110 javascript objects that we're familiar with and they have a bunch of key value pairs so name is Ira 116 00:07:57,110 --> 00:07:57,450 . 117 00:07:57,490 --> 00:08:00,530 Age is 24 city is Missoula. 118 00:08:00,530 --> 00:08:02,510 And then this is the really important part. 119 00:08:02,510 --> 00:08:06,040 Comments can just be nested right inside of the data. 120 00:08:06,110 --> 00:08:07,760 I don't have to deal with IDS. 121 00:08:07,850 --> 00:08:10,390 I don't have to define this table ahead of time. 122 00:08:10,490 --> 00:08:16,820 I can just nest comments in here and just start adding objects and if I recommit something else I can 123 00:08:16,820 --> 00:08:19,910 just add in another comment push into that array. 124 00:08:19,910 --> 00:08:27,360 And so this comment could say why does no one care about on Tanno. 125 00:08:27,790 --> 00:08:29,120 And that's a really good question. 126 00:08:29,150 --> 00:08:30,470 I don't know either. 127 00:08:30,590 --> 00:08:36,290 So we end up now with this very very flexible structure where if we wanted to I could just define favorite 128 00:08:36,290 --> 00:08:37,270 color down here. 129 00:08:37,400 --> 00:08:47,870 Fav color is purple and then I could have a whole other user who is named Tammy. 130 00:08:47,870 --> 00:08:52,900 And Tammy can be 24 from a zoo as well and she won't have a fave color at all. 131 00:08:52,910 --> 00:08:57,290 And instead she has favorite food which is revi. 132 00:08:57,320 --> 00:08:57,550 All right. 133 00:08:57,560 --> 00:08:58,740 So that's enough of that. 134 00:08:58,850 --> 00:09:05,060 But I really wanted to focus on with all of this is the difference between relational and non-relational 135 00:09:05,120 --> 00:09:10,730 so not the nitty gritty details of the syntax or how it actually works just the broad difference that 136 00:09:10,790 --> 00:09:14,920 sequel databases or relational databases have been around the longest. 137 00:09:15,010 --> 00:09:19,580 Are what most people think of when they think of databases where we have to define a table. 138 00:09:19,640 --> 00:09:25,520 Everything is tabular and if we want to relate data we have to have multiple tables to relate that data 139 00:09:25,610 --> 00:09:31,940 and we we often use IDs to do that with a non-relational database which is what we're going to be focusing 140 00:09:31,940 --> 00:09:34,040 on for most of this course. 141 00:09:34,130 --> 00:09:36,660 We don't have to define any sort of tables. 142 00:09:36,680 --> 00:09:41,930 We don't have tables at all actually and instead we have a much more flexible structure. 143 00:09:41,930 --> 00:09:45,390 Now this isn't to say that non-relational databases are better. 144 00:09:45,440 --> 00:09:50,990 In fact in a lot of cases they're not almost in all cases but there are specific situations where they 145 00:09:50,990 --> 00:09:55,490 make sense and I'll talk about why we're using a non-relational database in the next video. 146 00:09:55,490 --> 00:10:00,610 But I don't need to get the impression that because this is more flexible it's inherently better. 147 00:10:00,620 --> 00:10:05,600 That's not the case but it is more flexible which if that's what you're looking for then you want to 148 00:10:05,600 --> 00:10:07,590 use an non-relational database. 149 00:10:07,670 --> 00:10:09,580 All right so let's wrap this up. 150 00:10:09,650 --> 00:10:11,980 A database is a collection of information. 151 00:10:12,020 --> 00:10:17,330 It has an interface some sort of language some sort of technology or tools to interact with the data 152 00:10:17,480 --> 00:10:22,910 add new things read things out of the database delete things edit things and then there are two broad 153 00:10:22,910 --> 00:10:26,460 categories of databases sequel and no sequel. 154 00:10:26,840 --> 00:10:27,460 OK.