ename	VARCHAR2(10)
job	VARCHAR2O)
mgr	NUMBER(4) hiredate DATE
sal	NUMBER(7,2)
comm	NUMBER(7, 2)
dept	REF dept_type
     REF   (..       ),     .   ,      (   SQL)          .
,     dept_t    -      SELECT   DML.    SQL  ,   , ,         ,  dept_type    .
  , .. ,     CREATE TABLE OF TYPE,    .    ,          .
     .       .   ,          ,  ,       .     REF    ,    ,   REF,       (dangling) REF (..   ,    )        .
:
            ( , ,   -   ).       REF        REF.
    REF,    ,     :
UPDATE emp SET dept = (SELECT REF(d)
FROM dept_t d WHERE deptno = 10) WHERE empno = 7900;
5. 	99