Find those ratings for which the average age is the minimum over all ratings

• Aggregate operations cannot be nested! WRONG:

SELECT S.rating

FROM Sailors S

WHERE S.age = (SELECT MIN (AVG (S2.age)) FROM Sailors S2)

SELECT Temp.rating, Temp.avgage

FROM (SELECT S.rating, AVG (S.age) AS avgage

FROM Sailors S

GROUP BY S.rating) AS Temp

WHERE Temp.avgage = (SELECT MIN (Temp.avgage)

FROM Temp)

• Correct solution (in SQL/92):

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