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);
The answer is proxy server
A proxy server acts as an immediate or a gateway between you, the proxy client (example, the browser) and the internet or the destination website that you want to visit. Proxy servers are designed to re-route traffic and obscure source and destination. For instance, if you want to request a page like brainly, a proxy server will be able to retrieve this page for you by providing only its IP address to the site and act as a mediator between clients and the requested server. This however, does not mean that there is no link between you and this website. It means that all the information along with the requests you made will be collected by the proxy server.
Hi,
JVM - Java Virtual Machine
Hope this helps.
r3t40
Answer:
The answer is "14".
Explanation:
Let the IP address 
When it borrowed 4 bits
If the borrowed bits are left out then:
The Number of useable host addresses:
Answer:
The answer is (a).Presentation Layer
Explanation:
This layer is located at the 6th level of the OSI model, responsible for delivering and formatting the information to the upper layer for further processing. This service is needed because different types of computer uses different data representation. The presentation layer handles issues related to data presentation and transport, including encryption,translation and compression.
