SQL> 
SQL> -- XMLType view is similar to object view
SQL> -- This is a non-schema-based XMLType view
SQL> 
SQL> desc emp
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 EMPNO                                     NOT NULL NUMBER(4)
 ENAME                                              VARCHAR2(10)
 JOB                                                VARCHAR2(9)
 MGR                                                NUMBER(4)
 HIREDATE                                           DATE
 SAL                                                NUMBER(7,2)
 COMM                                               NUMBER(7,2)
 DEPTNO                                             NUMBER(2)

SQL> 
SQL> CREATE OR REPLACE VIEW Emp_view OF XMLTYPE WITH OBJECT ID
  2       (EXTRACT(sys_nc_rowinfo$,'/Emp/@empno').getnumberval())
  3         AS SELECT XMLELEMENT("Emp", XMLAttributes(empno),
  4              XMLForest(e.ename AS "name",
  5                         e.hiredate AS "hiredate")) AS "result"
  6            FROM emp e
  7            WHERE sal > 3000;

View created.

SQL> 
SQL> desc emp_view
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 TABLE of SYS.XMLTYPE 

SQL> -- Each row of an XMLType view corresponds to an XMLType instance
SQL> -- empno attribute in the document should become the unique identifier for each row.
SQL> -- SYS_NC_ROWINFO$ is a virtual column that references the row XMLType instance.
SQL> select * from emp_view;

SYS_NC_ROWINFO$                                                                 
--------------------------------------------------------------------------------
<Emp EMPNO="7839">                                                              
  <name>KING</name>                                                             
  <hiredate>17-NOV-81</hiredate>                                                
</Emp>                                                                          
                                                                                
<Emp EMPNO="1002">                                                              
  <name>DAVID</name>                                                            
  <hiredate>01-JAN-01</hiredate>                                                
</Emp>                                                                          
                                                                                
<Emp EMPNO="777">                                                               
  <name>jusung</name>                                                           
  <hiredate>01-JAN-03</hiredate>                                                
</Emp>                                                                          
                                                                                
<Emp EMPNO="1001">                                                              
  <name>JOHN</name>                                                             
  <hiredate>01-JAN-01</hiredate>                                                
</Emp>                                                                          
                                                                                

SQL> 
SQL> -- What's TYPE_TEXT_LENGTH?
SQL> -- Length of the type clause of the typed view.
SQL> -- Add and remove spaces behind 'XMLTYPE' in the view creation SQL and see what happens.
SQL> -- It does not mean much
SQL> select * from user_views where view_name='EMP_VIEW';

VIEW_NAME                      TEXT_LENGTH                                      
------------------------------ -----------                                      
TEXT                                                                            
--------------------------------------------------------------------------------
TYPE_TEXT_LENGTH                                                                
----------------                                                                
TYPE_TEXT                                                                       
--------------------------------------------------------------------------------
OID_TEXT_LENGTH                                                                 
---------------                                                                 
OID_TEXT                                                                        
--------------------------------------------------------------------------------
VIEW_TYPE_OWNER                VIEW_TYPE                                        
------------------------------ ------------------------------                   
SUPERVIEW_NAME                                                                  
------------------------------                                                  
EMP_VIEW                               197                                      
SELECT XMLELEMENT("Emp", XMLAttributes(empno),                                  
            XMLForest(e.ename AS "name",                                        
                       e.hiredate AS "hiredate")) AS "result"                   
          FROM emp e                                                            
          WHERE sal > 3000                                                      
               8                                                                
XMLTYPE                                                                         
             53                                                                 
EXTRACT(sys_nc_rowinfo$,'/Emp/@empno').getnumberval()                           
SYS                            XMLTYPE                                          
                                                                                
                                                                                

SQL> 
SQL> spool off