Exercise

Aggregate before joining tables

You have a list of the following items:

African athletes participating in past Olympics
Country GDP per capita
Population by year

For simplification, the annual demographics (GDP and population) have been grouped into low, medium, and high categories. Your job is to compare each African country's GDP, population, and athlete count.

You want the final answer to have one row per country, per year. Because the athletes table is on a different grain (athlete-event) than the demographics_rank table (country-year), you will first aggregate the athletes table before joining it to the GDP and population data.

Instructions 1/2

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Count the number of athletes by country and year using the athlete_id column.