How is IN different form EXISTS ?
IN executes the inner query for each row affected by the outer query and EXISTS executes the inner query only once irrespective of the outer query
IN executes the inner query only once irrespective of the outer query and EXISTS executes the inner query only once irrespective of the outer query
IN executes the inner query only once irrespective of the outer query and EXISTS executes the outer query for each row affected by the outer query
IN executes the inner query for each row affected by the outer query and EXISTS executes the outer query for each row affected by the outer query