semidifference via not in and a subqueryselect

Question

Semidifference via NOT IN and a subquery

SELECT StudentId

FROM IS_CALLED

WHERE Name = 'Devinder'

AND StudentId NOT IN (SELECT StudentId

FROM IS_ENROLLED_ON

WHERE CourseId = 'C1')

In above Example < > ALL replaces NOT IN and in the absence of NULL has the same effect. It reads, somewhat ambiguously, as "not equal to all". In fact the expression yields TRUE if and only if the condition comparing StudentId values is TRUE for every row in the result of the subquery.