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Next up, we're going to talk about logical or logical or is, I guess, a little bit like logical and

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only in the sense that we have a left in a right side that both will be evaluated and both can be different

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comparisons that we would make.

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But the end result is very different.

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So if we were to try this query here, select Star from Books where author last name is Eggers and release

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series Greater than 2010 and we've already done this, I'm just going to slim it down so that we only

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do title and author L name just so that we don't get that ugly formatting with my font size here.

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So we get those two books right.

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This is all from the last video.

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Both sides had to be true, last name had to be Eggers and release year had to be greater than 2010.

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But if I change that end to an OR with everything else exactly the same.

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So I'll just keep a record of both of them.

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But I'll change this to be in or.

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We'll get a very different result.

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So this result here contains all of the books that have an author name of Eggers.

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So there's those three or all of the books that have a release year greater than 2010.

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Now, we're actually not printing out the release here, so that is kind of screwing us up.

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Let's put that in here as well, because you can't tell for sure what's actually happening.

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Let's try that now.

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Now we can see all books by Eggers, but then also any book greater than or released after 2010.

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So we got 2016, 2014, 2017, and those are not written by Dave Eggers.

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So we're not satisfying this first comparison.

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But that's okay because we're using or the way that logical or works is that if we have a left and a

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right, only one of them has to be true in order for the whole thing to be considered true.

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In other words, in this example, if I'm MySQL going through all the rows and I check to see, okay,

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it's the author's last name Eggers on this row, if it is great, then we'll include that row.

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If it's not, well, what about this was it's released here greater than 2010.

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If that is true, then we'll also include the row.

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But again, if this was and instead both must be true.

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So we can use or in all sorts of ways, let me just demonstrate first how it behaves in the sort of

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vacuum of a logical operator, a very simple statement like this.

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So it's one less than five.

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We know that that's true.

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We get one.

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And if I do one, less than five or four is equal to five.

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Well, we know that this is not true, but we still get one because only one side of the or has to be

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true.

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If I change this to be an end now we get false because both sides have to be true.

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But this set is not.

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But if I had two false sides with my or like is one less than zero, that is false and the other side

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is false, the whole thing is false.

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So we still have to have one side be true.

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Here's a slide to summarize exactly what I just said with and both sides must be true.

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Both conditions with or only one side must be true.

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And then of course we could use or multiple times in the same way that we could have and multiple times

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like this example here and author last name is Eggers and title like novel.

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I could do the same thing with or so why don't we do an example where I'm going on a very short flight

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and I want to find the books that are short or the books that are short story collections, because

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I don't want to start a long novel and then get off my flight and never finish it.

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But if it's a collection of short stories, I can read one or two stories and it's these small discrete

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units, or if it's a short book, then I can just read the whole book.

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So we'll do something like select the title, the page count, and just do that for now from books.

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And my first condition is going to be where pages, let's say, is less than 200.

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So that will give me all of the books that are short.

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We've already done this query, I'm pretty sure.

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Interpreter of Maladies.

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What we talk about when we talk about love and Cannery Row.

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But I also want to do the short story collections, and those are the ones that include stories in their

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title.

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So I'll do an or title like and then percent stories and percent afterwards.

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Go back to the wild card or the like video if you're not sure what the percents are.

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But I want to see if stories is somewhere in the middle at the beginning or the end of the title.

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And now we get all the short books.

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198.

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Cannery Row 181.

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But also long books like Where I'm Calling From Selected Stories and Oblivion Stories.

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But they are stories.

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They include stories in their title, so they pass the test that we set up.

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Only one side had to be true.

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So for oblivion, this book down here stories.

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The first part is not true.

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It was 329 pages.

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That's false.

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But this part was true.

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So the whole thing is considered true.

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And we get that book, that row included in our results.

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So that's how we can use or one side or the other, they can both be true or only one has to be true

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in order for the whole thing to be true.