OracleµÄÓÅ»¯Æ÷ÓÐÁ½ÖÖÓÅ»¯·½Ê½(¶þ)

15. /*+USE_CONCAT*/
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ÀýÈç:
select /*+use_concat */ * from emp where deptno=10 OR empno=7788;
Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=2 Card=2 Bytes=174)
   1    0   TABLE ACCESS (FULL) OF 'EMP' (Cost=2 Card=2 Bytes=174)
16. /*+NO_EXPAND*/
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NO_EXPAND½«×èÖ¹Æä»ùÓÚÓÅ»¯Æ÷¶ÔÆä½øÐÐÀ©Õ¹.
SELECT /*+NO_EXPAND*/  *  from  EMP  WHERE DEPTNO=10 AND job='MANAGER';
Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=2 Card=1 Bytes=87)
   1    0   TABLE ACCESS (FULL) OF 'EMP' (Cost=2 Card=1 Bytes=87)
17. /*+NOWRITE*/
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18. /*+REWRITE*/
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19. /*+MERGE(TABLE)*/
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20. /*+NO_MERGE(TABLE)*/
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21. /*+ORDERED*/
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SELECT  /*+ORDERED*/  D.DNAME, E.ENAME,E.SAL from EMP E,DEPT D WHERE E.DEPTNO=D.DEPTNO;
Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=5 Card=82 Bytes=4510)
   1    0   HASH JOIN (Cost=5 Card=82 Bytes=4510)
   2    1     TABLE ACCESS (FULL) OF 'EMP' (Cost=2 Card=82 Bytes=2706)
   3    1     TABLE ACCESS (FULL) OF 'DEPT' (Cost=2 Card=82 Bytes=1804)
¶Ò»»ÏÂEMPºÍDEPTµÄ˳Ðò,µÃµ½
SELECT  /*+ORDERED*/  D.DNAME, E.ENAME,E.SAL from DEPT D, EMP E WHERE E.DEPTNO=D.DEPTNO;
Execution Plan
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