I have a query to "Find all courses taught in both the Fall 2009 semester and in the Spring 2010 semester" as
SELECT
course_id
FROM
section S
WHERE
semester = 'Fall'
AND YEAR = 2009
AND EXISTS (
SELECT
*
FROM
section T
WHERE
semester = 'Spring'
AND YEAR = 2010
AND S.course_id = T.course_id
);
In the second part of the where clause of the inner query you could see S.course_id=T.course_id
. What is S.course_id
? Is that the course_id
of the relation produced by the outer query ?
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