Please help on this question. Thank You! classroom (building, room number, capac

Question

Please help on this question. Thank You!

classroom (building, room number, capacity) department (dept name, building, budget) course (course id, title, dept name, credits) instructor (ID, name, dept name, salary) section (course id, sec id, semester, year, building, room number, time slot id) teaches(ID, course id, sec id, semester, year) student (ID, name, depl name, tot cred) takes(ID, course id, sec id, semester, year,grade) advisors ID, i-ID) time slot time slot id, day, start time, end time) prereq Courseld, prereg-do Figure 2.9 Schema of the university database.

Explanation / Answer

Here are the Answers of 4 queries for you:

Answer to a:

select ID, name,

count(course_id, sec_id, year,semester) as ‘Number of sections’

from instructor natural left outer join teaches

group by ID, name

Answer to b:

select ID, name,

(select count(*) as ‘Number of sections’

from teaches T where T.id = I.id)

from instructor I

Answer to c:

select course_id, sec_id, ID,

decode(name, NULL, ‘‘, name)

from (section natural left outer join teaches)

natural left outer join instructor

where semester=’Spring’ and year= 2010

Answer to d:

select dept_name, count(ID)

from department natural left outer join instructor

group by dept_name

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