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Exercise

Even more aliasing

Let's practice your newfound aliasing skills some more before moving on!

Recall: SQL assumes that if you divide an integer by an integer, you want to get an integer back.

This means that the following will erroneously result in 400.0:

SELECT 45 / 10 * 100.0;

This is because 45 / 10 evaluates to an integer (4), and not a decimal number like we would expect.

So when you're dividing make sure at least one of your numbers has a decimal place:

SELECT 45 * 100.0 / 10;

The above now gives the correct answer of 450.0 since the numerator (45 * 100.0) of the division is now a decimal!

Instructions 1/3
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  • 1

    Get the percentage of people who are no longer alive. Alias the result as percentage_dead. Remember to use 100.0 and not 100!

  • 2

    Get the number of years between the newest film and oldest film. Alias the result as difference.

  • 3

    Get the number of decades the films table covers. Alias the result as number_of_decades. The top half of your fraction should be enclosed in parentheses.

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