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We have one more of these aggregate functions we're going to cover, which is average.

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It's a really useful one.

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AVG, which is nice and short for average.

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It works in the same way we can find the average across all rows in a data set or we can group and then

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find averages.

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So to find the average release year across all books, it's as simple as select AVG released year.

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From books.

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And the average release here is 19 99.789, very close to 2000.

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But we could also do find the average number of pages across all the books.

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There we are, 362.

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Or how about the average stock quantity?

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128.9499474 OC.

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But of course we can also use group BI and do things like calculate the average stock quantity for books

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that have been released in the same year.

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So how would we do that?

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We would group buy released year and then select the average stock quantity.

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Let's try it.

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Let's select Released Year.

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Average Stock Quantity.

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And then from books group by released here.

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So we're grouping by the year that the books were released and then we're averaging their stock quantity.

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So in 2003, the average stock for those books that were released in that year is 66 2001.

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I know there is at least a couple of books.

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How would we know exactly how many books?

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Well, we can just put the count in as well.

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We can count the rows in each group.

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Count Star.

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So exactly what I thought.

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2001.

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There was three books released in that year.

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The average stock quantity is 134.3333.

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And that's all there is to average.

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It's a pattern.

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Hopefully you can recognize at this point, right some min max average count, you can use them on an

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entire table or use them in groups to find out more information about those groups.

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You can do a lot of analysis simply by creating different groups, grouping by different aspects of

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your data, and then using these different aggregate functions to query and figure out more about those

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groups.