Consider the following SQL query on the university schema:          select avg(salary)-(sum(salary) / count(*))           from instructor We might expect that the result of this query is zero since the average of a set of numbers is defined to be the sum of the numbers divided by the number of numbers. Indeed this is true for the example instructor

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Consider the following SQL query on the university schema:
         select avg(salary)-(sum(salary) / count(*))
          from instructor
We might expect that the result of this query is zero since the average of a set of numbers is defined to be the sum of the numbers divided by the number of numbers. Indeed this is true for the example instructor relation in Figure 2.1. However, there are other possible instances of that relation for which the result would not be zero. Give one such instance, and explain why the result would not be zero.

Schema Diagram for University Database
student
takes
ID
ID
course_id
sec_id
semester
уear
grade
пате
dept_name
tot_cred
section
course
department
dept name
building
budget
advisor
course_id
sec_id
semester
year
building
room_no
time_slot_id
course_id
title
dept_name
credits
s id
i id
time_slot
time slot_id
day
start_time
end_time
prereq
instructor
classroom
course_id
prereq_id
ID
building
room по
сараcity
пате
dept_name
salary
teaches
ID
course_id
sec id
semester
уear
Database System Concepts - 6th Edition
3.3
©Silberschatz, Korth and Sudarshan
Transcribed Image Text:Schema Diagram for University Database student takes ID ID course_id sec_id semester уear grade пате dept_name tot_cred section course department dept name building budget advisor course_id sec_id semester year building room_no time_slot_id course_id title dept_name credits s id i id time_slot time slot_id day start_time end_time prereq instructor classroom course_id prereq_id ID building room по сараcity пате dept_name salary teaches ID course_id sec id semester уear Database System Concepts - 6th Edition 3.3 ©Silberschatz, Korth and Sudarshan
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