Uncorrelated sub-query
A sub-query is another query within a query. The sub-query returns its results to an outer query to be processed.
You want a query that returns the region and countries that have experienced earthquakes centered at a depth of 400km or deeper. Your query will use the Earthquakes table in the sub-query, and Nations table in the outer query.
Este exercício faz parte do curso
Improving Query Performance in SQL Server
Exercício interativo prático
Experimente este exercício completando este código de exemplo.
SELECT UNStatisticalRegion,
CountryName
FROM Nations
WHERE ___ -- Country code for outer query
IN (SELECT ___ -- Country code for sub-query
FROM Earthquakes
WHERE ___ >= ___ ) -- Depth filter
ORDER BY UNStatisticalRegion;