17. What does on delete cascade clause do in the following SQL? CREATE TABLE enrollments (enrollment course no INT PRIMA

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17 What Does On Delete Cascade Clause Do In The Following Sql Create Table Enrollments Enrollment Course No Int Prima 1 (37.88 KiB) Viewed 17 times

17. What does on delete cascade clause do in the following SQL? CREATE TABLE enrollments (enrollment course no INT PRIMARY KEY AUTO INCREMENT, enrollment no VARCHAR(255) NOT NULL, FOREIGN KEY (enrollment no) REFERENCES courses (course_no) ON DELETE CASCADE All enrollments are deleted when the course is updated. All courses are deleted after enrollments are completed. All enrollment records are deleted automatically when the course is deleted. O All courses are deleted when enrollments for those courses are deleted. - What is the main advantage of a B tree index? O It is simpler than a hash table to implement. OIt uses hierarchal index to minimize the number of disk reads. It keeps keys in random order for traversing. OIt is optimized for systems that read and write small sets of data.