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  3. Improving Query Performance in SQL Server

Exercise

NOT IN with IS NOT NULL

You want to know which country capitals have never been the closest city to recorded earthquakes. You decide to use NOT IN to compare Capital from the Nations table, in the outer query, with NearestPop, from the Earthquakes table, in a sub-query.

Instructions 1/2

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  • Add the country capital name column to the outer query.
  • Add the city name column to the sub-query.
  • Check how many rows the query returns. Does this mean that earthquakes have been recorded near every capital city in the world?