For the view of Exercise 4.18, explain why the database system would not allow a tuple to be inserted into the database through this view.
For reference
For the database of Figure 4.12, write a query to find the ID of each employee with no manager. Note that an employee may simply have no manager listed or may have a null manager. Write your query using an outer join and then write it again using no outer join at all.
OUTER JOIN
select e.ID from employee e left outer join manages m on e.ID = m.ID
where m.manager_id is null;
NO OUTER
select e.ID from employee e where e.ID not in (select m.ID from manages m) or e.ID in (select m.ID from manages m where m.manager_id is null);
Any image that helps you, the reader, understand the text that the visual aid is accompanied with is referred to as a visual graphic or graphic aid.
Too frequently, readers lazily scan or entirely ignore graphs, diagrams, charts, and tables. Grid graphs, tables, bar charts, flow charts, maps, pie diagrams, and drawings and sketches are the most popular. Relationships are displayed using grid graphs. A visual aid should always be used in conjunction with preparation to interest the audience, improve their comprehension of your message, elicit an emotional response, and assist you in communicating it effectively. Charts, diagrams, graphs, maps, flashcards, posters, images, photos, booklets, folders, pamphlets, cartoons, and comics are examples of graphic aids.
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Explanation:
1.By Learning web development Fundamentals.
2.Choose a development specialization.
Answer:
#here is code in python.
# read the food bill
tot_bill=float(input("Please enter the food bill:"))
# tax on food
tax=0.06
#choice for tip by user
choice=int(input("enter your choice for tip:(1 for 15%, 2 for 18% and 3 for 20% :)"))
// calculate the total food bill
if choice==1:
tot_food_bill=tot_bill+tot_bill*tax+tot_bill*(.15)
elif choice==2:
tot_food_bill=tot_bill+tot_bill*tax+tot_bill*(.18)
elif choice==3:
tot_food_bill=tot_bill+tot_bill*tax+tot_bill*(.2)
else:
print("invalid choice:")
#print the total food bill
print("total food bill is ",tot_food_bill)
Explanation:
Read the food bill from user and assign it to variable "tot_bill".Initialize the tax=0.06 (i.e. 6%) on the bill.Then ask user to give his choice for tip. if the choice is 1 then tip will be 15%, if 2 then 18% and if choice is 3 Then tip will be 20% of the bill.Calculate the total food bill and assign it to variable "tot_food_bill".
Output:
Please enter the food bill:100
enter your choice for tip:(1 for 15%, 2 for 18% and 3 for 20% :)2
total food bill is 124.0
