SELECT c.cname
FROM Customers c
WHERE c.age > ALL (SELECT c2.age
FROM Customers c2
WHERE c2.type = 'snowboard');
SELECT c.cname
FROM Customers c
WHERE c.age > (SELECT MAX(c2.age)
FROM Customers c2
WHERE c2.type = 'snowboard')
它們看起來和我一樣,因爲MAX(c2.age)大於或等於列年齡中的所有值,並且如果c.age大於MAX(c2.age),則它大於所有值。爲什麼下面的SQL查詢不等效?
請標記dbms – McNets