<P> Currently hierarchical databases are still widely used especially in applications that require very high performance and availability such as banking and telecommunications . One of the most widely used commercial hierarchical databases is IMS . Another example of the use of hierarchical databases is Windows Registry in the Microsoft Windows operating systems . </P> <P> An organization could store employee information in a table that contains attributes / columns such as employee number, first name, last name, and department number . The organization provides each employee with computer hardware as needed, but computer equipment may only be used by the employee to which it is assigned . The organization could store the computer hardware information in a separate table that includes each part's serial number, type, and the employee that uses it . The tables might look like this: </P> <Table> <Tr> <Td> <Table> employee table <Tr> <Th> EmpNo </Th> <Th> First Name </Th> <Th> Last Name </Th> <Th> Dept . Num </Th> </Tr> <Tr> <Td> 100 </Td> <Td> Mahwish </Td> <Td> Faki </Td> <Td> 10 - L </Td> </Tr> <Tr> <Td> 101 </Td> <Td> Hamadh </Td> <Td> Hashim </Td> <Td> 10 - L </Td> </Tr> <Tr> <Td> 102 </Td> <Td> Nirun </Td> <Td> Ar </Td> <Td> 20 - B </Td> </Tr> <Tr> <Td> 103 </Td> <Td> fake </Td> <Td> Sandakelum </Td> <Td> 20 - B </Td> </Tr> </Table> </Td> <Td> <Table> computer table <Tr> <Th> Serial Num </Th> <Th> Type </Th> <Th> User EmpNo </Th> </Tr> <Tr> <Td> 3009734 - 4 </Td> <Td> Computer </Td> <Td> 100 </Td> </Tr> <Tr> <Td> 3 - 23 - 283742 </Td> <Td> Monitor </Td> <Td> 100 </Td> </Tr> <Tr> <Td> 2 - 22 - 723423 </Td> <Td> Monitor </Td> <Td> 100 </Td> </Tr> <Tr> <Td> 232342 </Td> <Td> Printer </Td> <Td> 100 </Td> </Tr> </Table> </Td> </Tr> </Table> <Tr> <Td> <Table> employee table <Tr> <Th> EmpNo </Th> <Th> First Name </Th> <Th> Last Name </Th> <Th> Dept . Num </Th> </Tr> <Tr> <Td> 100 </Td> <Td> Mahwish </Td> <Td> Faki </Td> <Td> 10 - L </Td> </Tr> <Tr> <Td> 101 </Td> <Td> Hamadh </Td> <Td> Hashim </Td> <Td> 10 - L </Td> </Tr> <Tr> <Td> 102 </Td> <Td> Nirun </Td> <Td> Ar </Td> <Td> 20 - B </Td> </Tr> <Tr> <Td> 103 </Td> <Td> fake </Td> <Td> Sandakelum </Td> <Td> 20 - B </Td> </Tr> </Table> </Td> <Td> <Table> computer table <Tr> <Th> Serial Num </Th> <Th> Type </Th> <Th> User EmpNo </Th> </Tr> <Tr> <Td> 3009734 - 4 </Td> <Td> Computer </Td> <Td> 100 </Td> </Tr> <Tr> <Td> 3 - 23 - 283742 </Td> <Td> Monitor </Td> <Td> 100 </Td> </Tr> <Tr> <Td> 2 - 22 - 723423 </Td> <Td> Monitor </Td> <Td> 100 </Td> </Tr> <Tr> <Td> 232342 </Td> <Td> Printer </Td> <Td> 100 </Td> </Tr> </Table> </Td> </Tr>

Which of the following is an examples of external databases in the data warehouse model
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