WEBVTT 00:00.210 --> 00:00.600 All right. 00:00.600 --> 00:02.330 Moving on to like this. 00:02.400 --> 00:08.640 So we've seen now users photos and comments and likes are a little bit similar. 00:08.670 --> 00:16.470 They are like the comments schema because when we think about how likes work on Instagram at least you 00:16.470 --> 00:19.130 like something you like that particular photo. 00:19.130 --> 00:22.230 Let's say it's corresponding to that photo. 00:22.260 --> 00:24.120 We need to have an association there. 00:24.540 --> 00:31.980 But then there's also the association between me the person liking it and the like itself. 00:32.280 --> 00:38.940 And that might not matter if we allowed for infinite likes you know anybody could like something as 00:38.940 --> 00:43.340 many times as they wanted to say it was a button that clicked and it just kept going every time I clicked 00:43.340 --> 00:43.760 it. 00:43.890 --> 00:48.670 We could get away with not storing user information with a like. 00:48.900 --> 00:53.850 But even then it might be nice to see how many times somebody had like something or how many likes you 00:53.850 --> 00:55.500 know in general. 00:55.500 --> 00:59.240 How often do I click the Like button compared to somebody else. 00:59.400 --> 01:04.020 It might be it might help us figure out who's a bot like on Instagram that's a big problem actually 01:04.020 --> 01:11.430 are these bots that people write they go and just like photos like things all the time create comments 01:11.430 --> 01:12.840 that are just cookie cutter. 01:13.200 --> 01:18.150 It's kind of frustrating actually if you're a photographer because you know you'll post something and 01:18.150 --> 01:24.480 then you get excited that you have you know 100 people who liked it and it turns out a lot of them are 01:24.480 --> 01:24.910 bought. 01:24.930 --> 01:28.760 If you actually go try and look at them they don't have any photos post really. 01:28.860 --> 01:30.750 They always comment the same thing. 01:30.750 --> 01:38.190 Long story short in this giant dataset here I actually coded in some bots that will be working with 01:38.460 --> 01:44.130 basically people who aren't in search who aren't creating much stuff they're not posting many photos 01:44.400 --> 01:49.470 but they are liking a lot of things and commenting on the same thing all the time. 01:49.470 --> 01:51.210 Anyway back to likes. 01:51.630 --> 01:59.310 It's going to look like this will have a user ID and a photo ID and a created app so our user ID is 01:59.310 --> 02:07.720 going to refer to a user's ID and a photo ID refer to a photo ID and there is really nothing else. 02:07.790 --> 02:10.330 Is no information being stored there. 02:10.440 --> 02:15.030 You know aside from the date or the time it was created when the like happened. 02:15.030 --> 02:17.030 But what else is there in store. 02:17.080 --> 02:23.430 You know maybe Instagram is doing stuff like whether it was liked from the web version versus the iOS 02:23.430 --> 02:24.120 version. 02:24.180 --> 02:29.810 Maybe they're storing you know other information here possibly but for us this is the basics. 02:29.820 --> 02:35.530 We just need a user ID and a photo ID and every time no photo is liked by a different user. 02:35.580 --> 02:40.300 We get a new like just like this with the user id and photo ID. 02:40.470 --> 02:42.030 So we'll start by coding this. 02:42.030 --> 02:45.610 You might have noticed that I didn't add an ID to the likes. 02:45.650 --> 02:47.060 Explain why in just a second. 02:47.340 --> 02:50.480 But let's start by creating our table. 02:50.770 --> 02:53.710 So we have create table like this. 02:54.390 --> 02:56.960 And don't forget the semi-colon. 02:57.120 --> 03:05.470 We've got a user ID and a photo ID and are created at headstart was created at we often neglect it. 03:05.520 --> 03:08.730 Time stamp the default now. 03:09.210 --> 03:09.600 OK. 03:09.600 --> 03:10.640 Nice and easy. 03:10.920 --> 03:13.790 User ID is just an integer. 03:14.200 --> 03:16.850 I don't want it to be empty. 03:16.860 --> 03:19.040 Same thing for photo ID. 03:20.320 --> 03:32.830 But then we need to set up our foreign key constraints for key user id references user's ID comma and 03:32.900 --> 03:35.430 other foreign key. 03:35.430 --> 03:41.580 This time photo ID references photos Id. 03:42.590 --> 03:47.400 OK so now let's address why we don't have an ID here. 03:47.400 --> 03:50.370 And the main reason is that we don't need an ID. 03:50.400 --> 03:53.800 We're not going to be referring to like anywhere else. 03:53.930 --> 04:00.570 If we were it would be good to add an ID there maybe but we're not having any table store information 04:00.570 --> 04:01.350 about likes. 04:01.350 --> 04:07.590 The other thing you might be wondering about is how do we ensure that you know there's only one like 04:07.600 --> 04:08.550 per user. 04:08.550 --> 04:10.290 Is there a way to do that in the database. 04:10.290 --> 04:18.030 Because right now if I did this I could just insert let's say my user ID is one and a photo ID is one 04:18.390 --> 04:23.430 I could insert a like with the user id one photo ID one and then insert it again and again and again. 04:23.760 --> 04:25.200 And there's nothing stopping that. 04:25.200 --> 04:30.480 So what we really want to say is we want a unique combination of the two. 04:30.570 --> 04:35.880 There can only be one instance of every combination and there's actually a way of saying that we haven't 04:35.880 --> 04:45.630 seen it but you can do this primary key and then we can just say use your ID comma photo ID. 04:45.690 --> 04:52.350 So what this will do is basically not allow you to insert to you know like that are exactly the same 04:52.650 --> 04:58.800 the same user ID and the same photo ID and I'll demonstrate that if you feel confident if you trust 04:58.800 --> 05:00.800 me there you can skip move on. 05:00.820 --> 05:02.260 We're done with the ski mask here. 05:02.410 --> 05:04.240 Let's just make sure that it runs. 05:04.290 --> 05:06.940 I don't have any syntax errors of course. 05:07.360 --> 05:08.050 OK. 05:08.320 --> 05:08.880 It does. 05:09.060 --> 05:12.640 But if you'd like to see me try it out like the last couple of videos. 05:12.640 --> 05:13.730 I'll do that now. 05:14.110 --> 05:21.280 So if you're still with me I'm going to do is take these photos and these users I'm going to have some 05:21.280 --> 05:22.100 of them like them. 05:22.240 --> 05:28.320 So let's take a blue user id one and that first photo she created it. 05:28.330 --> 05:29.270 That doesn't matter. 05:29.290 --> 05:31.180 You can like your own photo on Instagram. 05:31.360 --> 05:33.000 So will insert into likes 05:39.550 --> 05:43.610 and we have user id come a photo ID. 05:44.770 --> 05:51.500 So the first one will be one coming one so I'm inserting blue is liking this photo. 05:51.700 --> 05:53.900 And then let's have Charlie Brown also like it. 05:54.070 --> 05:59.260 So that would be a weps to come in one. 05:59.740 --> 06:05.710 And then we've got the next photo here which has a photo idea of two not this. 06:05.740 --> 06:07.820 Remember this is the user who created it. 06:08.050 --> 06:10.270 But this has an idea of two. 06:10.630 --> 06:12.890 So let's say blue also likes that one. 06:13.000 --> 06:19.810 So blue idea if one likes photo ID two and she likes photo ID of three. 06:19.870 --> 06:27.200 And then what say I have used already three I like photo with idea of three. 06:27.910 --> 06:28.480 OK. 06:29.140 --> 06:31.400 So let's start there. 06:32.650 --> 06:33.100 We run it. 06:33.100 --> 06:34.360 It works. 06:34.390 --> 06:36.220 There shouldn't be any problems at this point. 06:36.400 --> 06:44.100 But now if I try and do this insert into likes user id come a photo ID values. 06:44.170 --> 06:45.800 And I do one comma one. 06:45.940 --> 06:47.170 Well that's not that. 06:47.170 --> 06:51.060 There you go one come one which already is in there blue. 06:51.490 --> 06:52.960 User ID one. 06:53.470 --> 06:55.250 And then this photo. 06:55.330 --> 07:03.040 And while Bob 5:53 with idea of one we already have that like that if I try it you can see it duplicate 07:03.040 --> 07:06.000 entry 1 dash 1 for key primary. 07:06.220 --> 07:11.980 So the way it does it is basically combined to to keep track of the combination like that the dash between 07:11.980 --> 07:12.360 it. 07:12.370 --> 07:13.920 So that's pretty much it. 07:14.080 --> 07:18.560 I will copy what we just did an ad a note here. 07:19.030 --> 07:29.720 If you're looking at these notes later just saying it won't work because of primary key constraint and 07:29.740 --> 07:30.750 are commented out as well. 07:30.760 --> 07:32.500 We don't want to run that every time. 07:32.500 --> 07:33.190 Great. 07:33.200 --> 07:38.710 And next up we're moving on to a fun one which is relationships following followers all this stuff.