Consider the structure of the country table.
mysql> DESCRIBE Country;
Which of the following queries will return a list of all countries that have a larger population than their continent’s average?
A.
SELECT Name, Continent, Population
FROM Country
WHERE Population > (SELECT AVG(Population)
FROM Country
WHERE Continent=Continent
GROUP BY Continent)
B.
SELECT Name, Continent, Population
FROM Country
WHERE Population > (SELECT AVG(Population)
FROM Country
WHERE inner.Continent=outer.Continent
GROUP BY Continent)
C.
SELECT Name, Continent, Population
FROM Country AS Cl
WHERE Population > (SELECT AVG(Population)
FROM Country
WHERE Cl.Continent=Continent
GROUP BY Continent)
D.
SELECT Name, Continent, Population
FROM Country AS Cl
WHERE Population > (SELECT AVG(Population)
FROM Country AS C2
WHERE Cl.Continent=C2.Continent
GROUP BY Continent)
E.
You cannot use the same table in the inner and outer query of a subquery.
Explanation:
A ambiguous names, B inner and outer are ???,