It can penetrate the blood-brain barrier.
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);
<span>When you protect a workbook, you control the ability users have, to make changes to the file. This is t</span><span>o prevent other users from making changes, functions like adding, moving, deleting, or hiding worksheets, and renaming worksheets, you can </span>protect<span> it </span><span>with a password. </span>
