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Sometimes, we want to GROUP BY a calculation done on a column.

For instance, we might want to know how many movies have IMDb ratings that round to 1, 2, 3, 4, 5. We could do this using the following syntax:

SELECT ROUND(imdb_rating),
   COUNT(name)
FROM movies
GROUP BY ROUND(imdb_rating)
ORDER BY ROUND(imdb_rating);

However, this query may be time-consuming to write and more prone to error.

SQL lets us use column reference(s) in our GROUP BY that will make our lives easier.

and so on.

The following query is equivalent to the one above:

SELECT ROUND(imdb_rating),
   COUNT(name)
FROM movies
GROUP BY 1
ORDER BY 1;

Here, the 1 refers to the first column in our SELECT statement, ROUND(imdb_rating).

Suppose we have the query below:

SELECT category, 
   price,
   AVG(downloads)
FROM fake_apps
GROUP BY category, price;

Write the exact query, but use column reference numbers instead of column names after GROUP BY.

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