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So when we create a check constraint, which we've done twice, MySQL automatically comes up with a

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name for that constraint, which is what we see for our palindromes example palindromes underscore check

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C-H k underscore one is violated, so it just goes in order.

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If this is the first constraint that it finds and it's in the palindromes table, it's going to call

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it palindromes check one.

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If I had a second one, it would be palindromes check two, but we don't.

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So that, I guess, is fine.

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But what you'll see more often than not is a custom name added for the constraints.

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And that looks like this.

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We use the constraint keyword and then a name.

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And you generally keep this short.

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It's not going to be a whole message or something, but something like age over 18 and then the check

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and then whatever check expression we want.

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So this example is going to create the same check constraint as we had here for age.

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Age has to be greater than 18.

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But instead of being called parties, check one, the check constraint will be called age over 18.

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So then we'll see something like age over 18 violated, which is a little bit better.

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And also it makes it easier.

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If you ever wanted to remove a constraint, I'm going to show you how to alter tables later in this

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section.

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It's easier when you know the name is age over 18.

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Instead of having to guess partiers, check one or partiers check two.

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So let me show you this.

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Let's do the same thing for our users.

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So I'll keep the original version.

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And here's our second version where it will say age has to be greater than zero.

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I'm going to get rid of that and then do a constraint down here with the constraint keyword.

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We'll call it age positive or age not negative, whatever we want.

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Like that check and then age greater than I guess is equal to zero.

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Probably you can be zero years old and that should do it.

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And I already have a user's table, so I'll call this users too, which is stupid, but fine.

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And let's insert into users two and I'm just going to go ahead and insert something I know won't work.

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So let's have username age.

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And then values.

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How about, I don't know, Chicken lady and age will be negative nine.

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And what do we see?

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Check constraint.

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Age not negative is violated.

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So slightly better compare that to when I insert into the original users table, which has the same

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logic, but it's not a named constraint.

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Did I get rid of right here?

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This constraint here what we see is check constraint users check one is violated.

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Same logic behind the scenes, but this is easier to work with or at least understand what went wrong.

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So that's how we can add a name to a constraint.

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We could do the same thing for a palindromes.

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I don't know what we would call this though.

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Word has to be a var char and then constraint

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word.

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Is, pal.

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Maybe word is palindrome.

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Sure.

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And we'll call this palindromes, too.

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And I'll make this table.

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I need a comma.

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There.

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There we go.

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Let's go ahead and make this table here.

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Paste it in semicolon.

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So now, if I try an insert into palindromes to.

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Something that is not a palindrome.

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Like mom is a palindrome that should work.

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Just verify it does work.

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But Mama is not a palindrome.

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It's not the same forwards and backwards.

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It doesn't work.

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And this time we see Czech constraint.

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Word is palindrome is violated compared to if we did palindromes one or palindromes the original table,

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it just says palindromes check one is violated.

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So that's how we can add those custom names to a constraint.

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That also makes it easier.

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Like I said, if you want to remove those constraints later on once we talk about alter table.