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What happens when you want to
use more than one condition?

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Depending on what question you want
to ask, you can use either the AND

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keyword or the OR keyword.

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Let's look at a general example
first with one condition.

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To add a second condition you
add the appropriate keyword,

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then the next condition.

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Let's ask a question that
includes two conditions.

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What books in our library were authored
by J.K. Rowling before the year 2000?

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Let's remind ourselves of
the table's structure.

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We want to select the title, and
then we want to compare the author and

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the first_published columns.

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So, SELECT title FROM books

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WHERE author = "J.K.

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Rowling" AND

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first_published < 2000.

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Using the AND keyword means that
the row has to satisfy both conditions.

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If I were to swap it out with an OR,
it will retrieve books by J.K.

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Rowling OR
books first published before 2000.

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As you can see, using the wrong
keyword when combining conditions can

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present very different results.

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Let's ask another question.

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What books do we have in the library
authored by Ernest Klein or Andy Weir?

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Let's select author this time too.

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WHERE author = "Ernest Cline" OR

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author = "Andy Weir".

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We use OR rather than AND because the AND
tests if every condition is satisfied.

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Since the author cannot be both,
Ernest Cline or

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Andy Weir at the same time,
no results will come back.

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If we use OR
we don't mind which condition is true.

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As long as one of the conditions is true,
the row will be returned.

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To recap, the AND and OR keywords can
be used to chain conditions together.

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With the AND
keyword all conditions need to be met.

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With the OR keyword,
only one condition needs to be met.

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Combining the AND and OR keywords with
multiple conditions can get complex.

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I'll include some examples and details in
the teacher's notes for you to refer to.