5. Select the code that would show the countries with a greater GDP than any country in Africa (some countries may have NULL gdp values).
A.
SELECT name FROM bbc
WHERE gdp > ALL (SELECT MAX(gdp) FROM bbc WHERE region = 'Africa' AND gdp=0）
B.
SELECT name FROM bbc
WHERE gdp > (SELECT MAX(gdp) FROM bbc WHERE region = 'Africa')
C.
SELECT name FROM bbc
WHERE gdp > ALL (SELECT MIN(gdp) FROM bbc WHERE region = 'Africa')
D.
SELECT name FROM bbc
WHERE gdp > ALL (SELECT gdp FROM bbc WHERE region = 'Africa')
E.
SELECT name FROM bbc
WHERE gdp > ALL (SELECT gdp FROM bbc WHERE region = 'Africa' AND gdp<>NULL)
注：此题正确答案为B,但是我觉得D、E同样正确。
网址链接：https://sqlzoo.net/wiki/Nested_SELECT_Quiz
