ALL
<value> <op> ALL (<select_stmt>)
When the ALL
quantifier is used, the predicate is TRUE
if every value returned by the subquery satisfies the condition in the predicate of the main query.
Show only those clients whose ratings are higher than the rating of every client in Paris.
SELECT c1.*
FROM Customers c1
WHERE c1.rating > ALL
(SELECT c2.rating
FROM Customers c2
WHERE c2.city = 'Paris')
Important

If the subquery returns an empty set, the predicate is Nevertheless, it aligns perfectly with formal logic: if the set is empty, the predicate is true for every row in the set. 