8-1
mysql> select * from instructor where dept_name="Biology";
+-------+-------+-----------+----------+
| ID    | name  | dept_name | salary   |
+-------+-------+-----------+----------+
| 76766 | Crick | Biology   | 72000.00 |
+-------+-------+-----------+----------+
1 row in set (0.06 sec)

8-2
mysql> select * from course where dept_name="Comp. Sci." and credits="3"
    -> ;
+-----------+--------------------------+------------+---------+
| course_id | title                    | dept_name  | credits |
+-----------+--------------------------+------------+---------+
| CS-315    | Robotics                 | Comp. Sci. |       3 |
| CS-319    | Image Processing         | Comp. Sci. |       3 |
| CS-347    | Database System Concepts | Comp. Sci. |       3 |
+-----------+--------------------------+------------+---------+
3 rows in set (0.05 sec)

8-3
select course_id, title from course where course_id in (select course_id from takes where ID="12345");

select course.course_id, course.title from course natural join takes where ID="12345";

8-4
select sum(credits) from course natural join takes where ID="12345";

8-5
select id,sum(credits) from course natural join takes group by id;