WEBVTT 00:00.210 --> 00:02.110 All right you've got one more video here. 00:02.220 --> 00:08.370 And this has to do with managing triggers which sounds a bit like a chapter in a self-help book but 00:08.370 --> 00:14.280 really it has to do with how we make sure our triggers are working and mainly delete them. 00:14.430 --> 00:17.370 So this is where the name of our trigger comes into play. 00:17.520 --> 00:20.650 And then also I'll end with a quick warning about triggers. 00:20.970 --> 00:25.980 So the first thing that we can do is just list the triggers that exist in a database so we can just 00:25.980 --> 00:29.440 use show triggers to see what we have going on. 00:29.490 --> 00:31.890 And I'll warn you this is not my warning. 00:31.890 --> 00:39.330 I already talked about it but I'll warn you that what you get when you run this is kind of a mess to 00:39.330 --> 00:40.100 look at. 00:40.410 --> 00:45.200 But we can see we have in our Instagram data we have to triggers prevent cell follows. 00:45.270 --> 00:48.440 And then you can actually see the code inside of that trigger. 00:48.600 --> 00:52.740 And then we have capture unfollow and you can see that code as well. 00:52.740 --> 01:03.590 And if I switched over to the other database I believe it was use trigger demo and I do show triggers. 01:03.600 --> 01:04.760 We have one here. 01:04.860 --> 01:07.130 This is our must be adult. 01:07.410 --> 01:08.010 All right. 01:08.010 --> 01:12.290 So we have that I'll switch back to my Instagram clone. 01:17.150 --> 01:17.600 OK. 01:17.700 --> 01:20.600 And do our show triggers just to make sure they're still there. 01:20.670 --> 01:22.460 They shouldn't go anywhere anyways. 01:22.470 --> 01:24.060 But we've got two of them. 01:24.510 --> 01:26.640 So that's pretty much it to listing them. 01:26.670 --> 01:27.520 Moving on. 01:27.840 --> 01:31.380 So if I want to remove a trigger it's pretty simple. 01:31.380 --> 01:35.040 It's drop trigger and then the trigger name. 01:35.190 --> 01:36.660 So let's go back. 01:36.670 --> 01:39.850 Let's say I want to remove this prevent cell follows. 01:39.870 --> 01:42.660 I want to allow users to follow themselves. 01:42.780 --> 01:44.290 So I want to get rid of that. 01:44.370 --> 01:46.820 I'll just copy the name just so I don't have to type it. 01:47.430 --> 01:53.340 And we just do drop trigger pre-event cell follows. 01:53.700 --> 01:56.840 And if we do our show triggers again it's gone. 01:56.850 --> 02:04.110 And just to verify that it works it's not just the leading trigger from show triggers lets try and trigger 02:04.110 --> 02:10.060 it if you will with something that would have caused a problem or thrown an error in the past. 02:10.170 --> 02:18.710 So insert into follows and we have follow word I.D. come follow me. 02:18.950 --> 02:19.900 This is the worst part 02:23.640 --> 02:24.320 values. 02:24.360 --> 02:27.960 Let's Insearch one thing where they're the same. 02:27.960 --> 02:30.550 How about seven and seven. 02:32.010 --> 02:32.910 No problem. 02:32.970 --> 02:37.720 So in the past that would have been a problem because that trigger but it's now gone. 02:38.070 --> 02:38.490 OK. 02:38.490 --> 02:42.460 So that's really all there is to managing triggers or at least all that I'm going to talk about here. 02:42.540 --> 02:47.020 We can look at them using show and we can delete them using dropping trigger. 02:47.420 --> 02:53.520 So that brings me to the last thing that I warned you about which is I wanted to just briefly address 02:53.520 --> 02:56.120 a potential pickup with triggers. 02:56.160 --> 03:02.040 This is kind of a concern that a lot of developers have and it has to do with debugging code debugging 03:02.040 --> 03:05.640 applications that make use of triggers in your database. 03:05.640 --> 03:11.190 So imagine that you're a developer on a team with a bunch of people and something's not working how 03:11.190 --> 03:12.270 you expect it to. 03:12.480 --> 03:19.260 Let's say when you insert something into a table you realize that actually two items are being created 03:19.260 --> 03:21.460 for some reason and you have no idea why. 03:21.720 --> 03:26.310 And you might think OK maybe that something happening on my side of the application maybe that's my 03:26.310 --> 03:32.860 code that's that something is wrong you know with our logic on the front end with our let's say Objective 03:32.860 --> 03:38.850 C code and you could scour that forever but you would actually never get to the core of the problem 03:39.240 --> 03:46.260 if it was because of a trigger and triggers are kind of stealth little bugs waiting to happen because 03:46.470 --> 03:50.780 you have no way of identifying that something is happening because of a trigger. 03:50.850 --> 03:53.650 It happens kind of behind the scenes like remember. 03:53.680 --> 04:00.570 Go back here with our unfollow if I can go find that way back here. 04:00.600 --> 04:01.820 Oh boy where is that. 04:02.860 --> 04:04.180 Here we go. 04:04.240 --> 04:11.770 Here we had ninety nine entries created automatically when all they did was run a single line of sequel 04:11.770 --> 04:16.360 to actually delete things and ended up creating 99 things. 04:16.360 --> 04:17.830 Now we knew that was going to happen. 04:17.950 --> 04:24.670 But if you have a bunch of triggers and somebody doesn't know about I'm on team or you forget about 04:24.670 --> 04:29.710 them it can make things difficult to debug because it's basically magic happening behind the scenes 04:29.950 --> 04:31.030 things that are hidden. 04:31.180 --> 04:37.030 Typically you know when you're debugging your code is up in front of you you can see where the problems 04:37.030 --> 04:37.810 are happening. 04:38.080 --> 04:43.960 So triggers cause problems sometimes because of that and the other thing I would say is that some people 04:43.960 --> 04:46.970 have a tendency to chain triggers together. 04:47.020 --> 04:51.320 So with unfollowed example you could have another event trigger. 04:51.370 --> 04:56.290 So let's say here were one follow is deleted. 04:56.340 --> 04:58.110 We're inserting into an follows. 04:58.110 --> 05:03.790 We could have another trigger for when something is inserted into unfollowed to do something else. 05:03.900 --> 05:08.460 And you can chain them together and there's actually situations where believe it or not that actually 05:08.460 --> 05:11.900 makes sense but it's kind of frowned upon by a lot of people. 05:11.910 --> 05:14.640 So just be conscientious if you're using a lot of triggers. 05:14.670 --> 05:19.180 Typically there's a better way of doing it without having to make use of triggers. 05:19.230 --> 05:23.310 And if there's not then you know that it's a good use case for triggers. 05:23.310 --> 05:25.320 I'm not saying you should never use them. 05:25.410 --> 05:27.370 By all means they're very useful. 05:27.420 --> 05:31.910 It's just that you should be conscientious about them and try and find ways to not use them. 05:32.100 --> 05:32.360 OK. 05:32.370 --> 05:33.440 So to wrap that up. 05:33.600 --> 05:40.500 Just be aware that triggers can make debugging more difficult more problematic because stuff happens 05:40.500 --> 05:41.320 behind the scenes. 05:41.340 --> 05:43.720 It's not explicit when something happens. 05:43.860 --> 05:50.280 And then also be aware that too many triggers can often be a problem and you want to avoid triggers 05:50.790 --> 05:52.070 as much as you can. 05:52.110 --> 05:54.350 Not at all costs or anything I'm not saying they're bad. 05:54.360 --> 05:55.640 Just be careful with them. 05:55.830 --> 05:56.120 All right. 05:56.130 --> 05:58.610 So that answer some of your questions about triggers. 05:58.740 --> 06:04.200 Hopefully you can see the utility in them and I know a lot of people are asking about preventing people 06:04.200 --> 06:05.410 from following themselves. 06:05.520 --> 06:10.680 So if nothing else hopefully it's nice to see that how you can actually prevent people from following 06:10.680 --> 06:11.720 their stuff. 06:11.730 --> 06:12.310 All right.