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<v ->Hi, guys, welcome back.</v>

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In this video I wanted to tell you real quick

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about the HAVING clause.

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It is used for filtering after aggregation.

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So, the HAVING clause is used

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for filtering after aggregation.

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The WHERE clause is used for filtering before aggregation.

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So if you wanted to do something like this,

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SELECT poll_id and the COUNT of IDs,

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FROM options, GROUP BY poll_id,

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WHERE the option_count is greater than two.

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Notice that here we're using the aggregation column

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in the WHERE clause.

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Then you're gonna get an error.

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You can't do that.

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The WHERE clause is only for filtering before aggregation.

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You can do this though.

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SELECT poll_id and COUNT of id AS option_count if you want,

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FROM options, GROUP BY poll-id,

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HAVING COUNT of id greater than two.

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Something important to note here

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is COUNT id does not run twice.

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There's no performance problem here.

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This is just the syntax used.

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You can't use the alias column here,

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but that's just simply how it's done.

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But again, no performance problem there.

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This is everything for this video.

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Just wanted to tell you how HAVING and WHERE differ.

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Thanks for joining me in this one.

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Thank you for watching and I see you in the next one.