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We have one last very simple comparison function or operator actually that I'm going to show you, and

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it has to do with null values.

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So right now I have some null values in my books table like, well, these rows here have no author.

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How would I target those rows?

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Let's say I want to delete them or I want to just select them like select star from books.

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Let's say where the author last name is null.

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Well, it does not work to do this equals null.

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I don't get anything back.

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So instead of that, I have to use a special operator called is null.

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We also have is not null and this is set up to work specifically with null values.

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So instead of saying where all the last name is, equal sign no I'll say is null.

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And now we find all of the books that have no last name, where the last name is set to no great.

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I also have is not null.

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So same thing, but opposite.

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Now I'm getting back all the books that do have another last name that is not.

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No.

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So I guess we could end by deleting all of the books that have no author, last name or no title.

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And again, the way that I like to do that is by starting with a selection, select what I'm trying

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to delete and then delete.

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So select star from books.

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Where are we going to do title is null or last name?

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Let's do title.

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So I have two books that have no title.

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Let's delete them.

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So instead of select star from books where title is null, I'm going to do delete.

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From books where title is null and it says two rows affected.

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If I try and select those rose again, they're gone.

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So just a quick example of using is null and is not null.

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We can't directly compare using the equal sign to null or not equals.

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Really we need to use is null.

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End is not null.