SQL Movie-Rating View Modification Exercises Part B
SQL Movie-Rating View Modification Exercises Part B
This is the second part of the SQL Movie-Rating View Modification Exercises Part A
Question 6
Write an instead-of trigger that enables deletions from view HighlyRated.
Policy: Deletions from view HighlyRated should update all ratings for the corresponding movie that have stars > 3 so they have stars = 3.
Policy: Deletions from view HighlyRated should update all ratings for the corresponding movie that have stars > 3 so they have stars = 3.
create trigger Q6
instead of delete on HighlyRated
for each row
begin
update Rating
set stars = 3
where mID = Old.mID and stars>3 ;
end;
instead of delete on HighlyRated
for each row
begin
update Rating
set stars = 3
where mID = Old.mID and stars>3 ;
end;
Question 7
Write an instead-of trigger that enables insertions into view HighlyRated.
create trigger Q7
instead of insert on HighlyRated
for each row
when New.mID in (Select mID from Movie where mID = new.mID and title =
New.title)
begin
insert into Rating values (201, New.mID, 5, null);
end;
instead of insert on HighlyRated
for each row
when New.mID in (Select mID from Movie where mID = new.mID and title =
New.title)
begin
insert into Rating values (201, New.mID, 5, null);
end;
Question 8
Write an instead-of trigger that enables insertions into view NoRating.
create trigger Q8
instead of insert on NoRating
for each row
when New.mID in (Select mID from Movie where mID = new.mID and title =
New.title)
begin
delete from Rating where mID=New.mID;
end;
instead of insert on NoRating
for each row
when New.mID in (Select mID from Movie where mID = new.mID and title =
New.title)
begin
delete from Rating where mID=New.mID;
end;
Question 9
Write an instead-of trigger that enables deletions from view NoRating.
create trigger Q9
instead of delete on NoRating
for each row
begin
delete from Movie where mID=Old.mID;
end;
instead of delete on NoRating
for each row
begin
delete from Movie where mID=Old.mID;
end;
Question 10
Write an instead-of trigger that enables deletions from view NoRating.
create trigger Q10
instead of delete on NoRating
for each row
begin
Insert into Rating Values (201,old.mID,1,null);
end;
instead of delete on NoRating
for each row
begin
Insert into Rating Values (201,old.mID,1,null);
end;
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