SQL question | GameDev.net

This is a completely game-unrelated question, but I found it as an exercise on a text book I was reading and I don't have anyone else to ask right now, so here it goes: Given the following tables:

students = (id, name, age)
classes = (name, classrom_number)
inscriptions = (student_id, class_name)

and the following SQL query:

SELECT name
FROM students
WHERE NOT EXIST(SELECT *
                FROM inscriptions
                WHERE NOT EXIST(SELECT *
                                FROM classes
                                WHERE classes.name = class_name AND
                                student_id = id))

determine what the query informs. It seems to me that this query is wrong as the "student_id = id" condition in the innermost sub-query does not refer to the classes table which the query selects from, so this whole query shoudl either return an empty set or an error. Am I right?... Or maybe I don't fully understand SQL? [edited by - Night Elf on April 16, 2004 6:31:44 PM]

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