Generate nested xml

Question

I have following tables :
DEPT
DEPT_ID    DEPT_NAME      GRP_NAME
1          Engineering    Research and Development
2          Tool Design    Research and Development
EMP
EMP_ID      FIRST_NAME    MIDDLE_NAME    LAST_NAME     DEPT_ID    HIRE_DATE      
1           Roberto       Luc            Tamburello    1          1997-12-12     
2           Rob           (null)         Walters       2          1998-01-05     
3           Thierry       (null)         D'Hers        2          1998-01-11     
4           Janice        B.             Galvin        2          2001-01-23     
EMP_TEL
EMP_ID    TEL_ID
1         1
1         5
2         2
3         3
4         4
TEL
TEL_ID    AREA_CODE    PHONE_NO    EXT     TEL_TYPE_ID    
1         111          1111111     111     1
2         222          2222222     222     1
3         333          3333333     333     1
4         444          4444444     444     1
5         555          5555555     (null)  2
TEL_TYPE
TEL_TYPE_ID    TEL_TYPE_CD
1              OFFICE
2              FAX
3              CELLIs there a way to generate below xml in one sql statement?
<Company>
  <Department>
    <DepartmentName>Engineering</DepartmentName>
    <GroupName>Research and Development</GroupName>
    <Employee>
      <FirstName>Roberto</FirstName>
      <MiddleName>Luc</MiddleName>
      <LastName>Tamburello</LastName>
      <HireDate>1997-12-12</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>111-111-1111</TelephoneNumber>
        <Extension>111</Extension>
      </Telephone>
      <Telephone>
        <TelephoneType>FAX</TelephoneType>
        <TelephoneNumber>555-555-5555</TelephoneNumber>
      </Telephone>
    </Employee>
  </Department>
  <Department>
    <DepartmentName>Tool Design</DepartmentName>
    <GroupName>Research and Development</GroupName>
    <Employee>
      <FirstName>Rob</FirstName>
      <LastName>Walters</LastName>
      <HireDate>1998-01-05</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>222-222-2222</TelephoneNumber>
        <Extension>222</Extension>
      </Telephone>
    </Employee>
    <Employee>
      <FirstName>Thierry</FirstName>
      <LastName>D'Hers</LastName>
      <HireDate>1998-01-11</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>333-333-3333</TelephoneNumber>
        <Extension>333</Extension>
      </Telephone>
    </Employee>
    <Employee>
      <FirstName>Janice</FirstName>
      <MiddleName>B.</MiddleName>
      <LastName>Galvin</LastName>
      <HireDate>2001-01-23</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>444-444-4444</TelephoneNumber>
        <Extension>444</Extension>
      </Telephone>
    </Employee>
  </Department>
</Company>

Answer 1

Is there a way to generate below xml in one sql statement?yes, this way:
SQL> select xmlelement("Company",
  2               xmlagg(
  3                  xmlelement("Department",
  4                             xmlforest(dept_name as "DepartmentName",
  5                                       grp_name as "GroupName"
  6                                       ),
  7                             (select xmlagg(
  8                                         xmlelement("Employee",
  9                                                    xmlforest(FIRST_NAME as "FirstName",
10                                                              MIDDLE_NAME as "MiddleName",
11                                                              LAST_NAME as "LastName",
12                                                              to_char(HIRE_DATE,'yyyy-mm-dd') as "HireDate"
13                                                              ),
14                                                    (Select xmlagg(
15                                                              xmlelement("Telephone",
16                                                                         xmlforest(TEL_TYPE_CD as "TelephoneType",
17                                                                                   AREA_CODE||'-'||PHONE_NO as "TelephoneNumber",
18                                                                                   EXT as "Extension"
19                                                                                   )
20                                                                         )
21                                                                   )
22                                                        from TEL t, TEL_TYPE tt, EMP_TEL et
23                                                       where t.TEL_TYPE_ID=tt.TEL_TYPE_ID
24                                                         and et.EMP_ID = e.EMP_ID
25                                                         and et.TEL_ID = t.TEL_ID
26                                                    )
27                                                   )
28                                              )
29                                from emp e
30                               where e.DEPT_ID=d.DEPT_ID
31                              )
32                             )
33                      )
34                    ).extract('/*') doc
35    from DEPT d;
DOC
<Company>
  <Department>
    <DepartmentName>Engineering</DepartmentName>
    <GroupName>Research and Development</GroupName>
    <Employee>
      <FirstName>Roberto</FirstName>
      <MiddleName>Luc</MiddleName>
      <LastName>Tamburello</LastName>
      <HireDate>1997-12-12</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>111-1111111</TelephoneNumber>
        <Extension>111</Extension>
      </Telephone>
      <Telephone>
        <TelephoneType>FAX</TelephoneType>
        <TelephoneNumber>555-5555555</TelephoneNumber>
      </Telephone>
    </Employee>
  </Department>
  <Department>
    <DepartmentName>Tool Design</DepartmentName>
    <GroupName>Research and Development</GroupName>
    <Employee>
      <FirstName>Rob</FirstName>
      <LastName>Walters</LastName>
      <HireDate>1998-01-05</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>222-2222222</TelephoneNumber>
        <Extension>222</Extension>
      </Telephone>
    </Employee>
    <Employee>
      <FirstName>Thierry</FirstName>
      <LastName>D&apos;Hers</LastName>
      <HireDate>1998-01-11</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>333-3333333</TelephoneNumber>
        <Extension>333</Extension>
      </Telephone>
    </Employee>
    <Employee>
      <FirstName>Janice</FirstName>
      <MiddleName>B.</MiddleName>
      <LastName>Galvin</LastName>
      <HireDate>2001-01-23</HireDate>
      <Telephone>
        <TelephoneType>OFFICE</TelephoneType>
        <TelephoneNumber>444-4444444</TelephoneNumber>
        <Extension>444</Extension>
      </Telephone>
    </Employee>
  </Department>
</Company>Max
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