3.11
答案自行小写：
# a.
SELECT `name`
FROM student NATURAL JOIN takes NATURAL JOIN course
WHERE dept_name = 'Comp. Sci.'
# b.
SELECT `ID`, `name`
FROM student
EXCEPT
SELECT `ID`, `name`
FROM student NATURAL JOIN takes
WHERE `year` < 2009
# c.
SELECT `dept_name`, MAX(salary)
FROM instructor
GROUP BY dept_name
#d.
SELECT MAX(salary)
FROM
(SELECT `dept_name`, MAX(salary)
FROM instructor
GROUP BY dept_name)
3.12
# a.
INSERT INTO course
VALUES('CS-001', 'Weekly Seminar', 'Comp. Sci.', 0)
# b.
INSERT INTO section(`year`, semester, sec_id)
VALUES('2009', 'Fall', 1)
# c.
INSERT INTO takes
SELECT ID, 'CS-001', 1, 'Fall', '2009', NULL
FROM student
WHERE dept_name = 'Comp. Sci.'
# d.
DELETE FROM takes
WHERE course_id = 'CS-001' AND sec_id = 1 AND semester = 'Fall' AND `year` = 2009
AND ID IN
(SELECT ID
FROM student
WHERE `name` = 'Chavez')
# e.
DELETE FROM takes
WHERE course_id = 'CS-001'
DELETE FROM section
WHERE course_id = 'CS-001'
DELETE FROM course
WHERE course_id = 'CS-001'
#上面的顺序不能改变，因为takes的course_id外码依赖于section，
# section的course_id外码依赖于course，改变顺序会导致外码冲突
# f.
DELETE FROM takes
WHERE course_id IN
(SELECT course_id
FROM course
WHERE LOWER(title) LIKE '%database%')
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原文链接：https://blog.csdn.net/qq_43212582/article/details/105392877