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);
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Answer:
MULTITASKING OS
Explanation:
MULTITASKING OPERATING SYSTEM is an operating system that enables and allow user of either a smartphone or computer to make use of more that one applications program at a time.
Example with MULTITASKING OPERATING SYSTEM smartphones user can easily browse the internet with two applications program like chrome and Firefox at a time or simultaneously
Therefore a user working with two apps simultaneously is an example of a unit that uses a MULTITASKING OS.
Answer:
just go ahead and refresh the page
Explanation:
