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Exercise

Practice with COUNT

As you've seen, COUNT(*) tells you how many rows are in a table. However, if you want to count the number of non-missing values in a particular column, you can call COUNT() on just that column.

For example, to count the number of birth dates present in the people table:

SELECT COUNT(birthdate)
FROM people;

It's also common to combine COUNT() with DISTINCT to count the number of distinct values in a column.

For example, this query counts the number of distinct birth dates contained in the people table:

SELECT COUNT(DISTINCT birthdate)
FROM people;

Let's get some practice with COUNT()!

Instructions 1/5
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  • 1

    Count the number of rows in the people table.

  • 2

    Count the number of (non-missing) birth dates in the people table.

  • 3

    Count the number of unique birth dates in the people table.

  • 4

    Count the number of unique languages in the films table.

  • 5

    Count the number of unique countries in the films table.

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