oracle exists and not exist

ÏÈ¿´ÏÂÃæµÄÀý×Ó:oracleÖÐÁ½¸öϵͳ±í.emp,dept.
example:
1:not exists(not in)
not exists:
   ÕâÌõÓï¾ä·µ»Øselect * from scott.dept d where e.deptno=d.deptno and d.deptno=10Ìõ¼þÂú×ãµÄ½á¹û¼¯.Ò²¾ÍÊÇ˵,
·µ»ØµÄ½á¹û¼¯Öв»´æÔÚd.deptno=10½á¹û¼¯µÄ¼Ç¼,¼´emp±íÖÐûÓÐdept±íÖÐd.deptno=10µÄ¼Ç¼.
SQL> select empno,ename,deptno from scott.emp e where not exists(select * from scott.dept d where e.deptno=d.deptno and d.deptno=10);
EMPNO ENAME      DEPTNO
----- ---------- ------
 7369 SMITH           20
 7499 ALLEN           30
 7521 WARD           30
 7566 JONES           20
 7654 MARTIN         30
 7698 BLAKE           30
 7788 SCOTT           20
 7844 TURNER         30
 7876 ADAMS          20
 7900 JAMES           30
 7902 FORD            20
11 rows selected
not in:
µÚÒ»¸öwhereÌõ¼þ±ØÐë¸ø¶¨×Ö¶Î(deptno), µÚ¶þ¸ösqlÓï¾äÖÐ,±ØÐëÃ÷È·¸ø¶¨Òª²éѯµÄ×Ö¶ÎÊÇÄĸö(deptno).
SQL> select empno,ename,deptno from scott.emp e where deptno not in(select deptno from scott.dept d where e.deptno=d.deptno and d.deptno=10);
EMPNO ENAME      DEPTNO
----- ---------- ------
 7369 SMITH           20
 7499 ALLEN           30
 7521 WARD           30
 7566 JONES