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All right.

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So we've got one more video here.

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And this has to do with managing triggers, which sounds a bit like a chapter in a self-help book.

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But really, it has to do with how we make sure our triggers are working and mainly delete them.

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So this is where the name of our trigger comes into play.

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And then also I'll end with a quick warning about triggers.

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So the first thing that we can do is just list the triggers that exist in a database so we can just

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use show triggers to see what we have going on.

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And I'll warn you, this is not my warning I already talked about, but I'll warn you that what you

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get when you run this is kind of a mess to look at.

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But we can see we have in our Instagram data, we have two triggers prevent self follows, and then

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you can actually see the code inside of that trigger.

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And then we have captured Unfollow and you can see that code as well.

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And if I switched over to the other database, I believe it was used trigger demo.

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And I do show triggers.

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We have one here.

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This is our must be adult.

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All right, so we have that.

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I'll switch back to my Instagram clone.

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OC and do our show triggers just to make sure they're still there.

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They shouldn't go anywhere anyways, but we've got two of them, so that's pretty much it to listing

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them.

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Moving on.

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So if I want to remove a trigger, it's pretty simple.

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It's drop trigger and then the trigger name.

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So let's go back.

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Let's say I want to remove this prevent self follows.

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I want to allow users to follow themselves.

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So I want to get rid of that.

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I'll just copy the name just so I don't have to type it.

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And we just do drop trigger prevent self follows.

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And if we do our show triggers again, it's gone.

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And just to verify that it works, it's not just deleting the trigger from show triggers.

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Let's try and trigger it, if you will, with something that would have caused a problem or thrown an

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error in the past.

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So insert into follows and we have follower ID comma follow we just the worst part.

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Values.

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So let's insert something where they're the same.

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How about seven and seven?

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No problem.

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So in the past, that would have been a problem because of that trigger, but it's now gone.

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So that's really all there is to managing triggers or at least all that I'm going to talk about here.

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We can look at them using show and we can delete them using drop trigger.

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So that brings me to the last thing that I warned you about, which is I wanted to just briefly address

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a potential hiccup with triggers.

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This is kind of a concern that a lot of developers have, and it has to do with debugging code debugging

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applications that make use of triggers in your database.

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So imagine that you're a developer on a team with a bunch of people and something's not working how

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you would expect it to.

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Let's say when you insert something into a table, you realize that actually two items are being created

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for some reason and you have no idea why.

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And you might think, okay, maybe that's something happening on my side of the application.

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Maybe that's my code.

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That's, that's something is wrong with our logic on the front end with our, let's say, Objective-C

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code.

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And you could scour that forever, but you would actually never get to the core of the problem if it

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was because of a trigger.

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And triggers are kind of stealth little bugs waiting to happen because you have no way of identifying

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that something is happening because of a trigger.

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It happens kind of behind the scenes.

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Like, remember, if we go back here with our unfollow, if I can go find that way back here.

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Oh, boy.

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Where is that?

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Here we go.

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Here we had 99 entries created automatically when all I did was run a single line of SQL to actually

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delete things.

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It ended up creating 99 things.

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Now we knew that was going to happen, but if you have a bunch of triggers and somebody doesn't know

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about them on the team or you forget about them, it can make things difficult to debug because it's

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basically magic happening behind the scenes things that are hidden.

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Typically when you're debugging, your code is up in front of you.

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You can see where the problems are happening.

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So triggers cause problems sometimes because of that.

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And the other thing I would say is that some people have a tendency to chain triggers together.

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So with our unfollow example, you could have another event trigger.

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So let's say.

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Here.

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When a follow is deleted, we're inserting into unfollow those.

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We could have another trigger for when something is inserted into unfollow us to do something else and

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you can chain them together.

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And there's actually situations where, believe it or not, that actually makes sense, but it's kind

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of frowned upon by a lot of people.

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So just be conscientious.

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If you're using a lot of triggers, typically there's a better way of doing it without having to make

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use of triggers.

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And if there's not, then you know that it's a good use case for triggers.

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I'm not saying you should never use them, but by all means they're very useful.

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It's just that you should be conscientious about them and try and find ways to not use them.

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So to wrap that up, just be aware that triggers can make debugging more difficult, more problematic,

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because stuff happens behind the scenes.

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It's not explicit when something happens, and then also be aware that too many triggers can often be

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a problem.

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And you want to avoid triggers as much as you can.

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Not at all costs or anything.

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I'm not saying they're bad.

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Just be careful with them.

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All right.

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So hopefully that answers some of your questions about triggers.

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Hopefully you can see the utility in them.

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And I know a lot of people are asking about preventing people from following themselves.

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So if nothing else, hopefully it's nice to see that how you can actually prevent people from following

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themselves.

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All right.