今天测试了oracle的hints,由于之前数据库没有建好temporary表空间，所以重新添加了（相关命令如下）：
@/oracle/app/oracle/product/10g/db_1/sqlplus/admin/plustrce.sql grant plustrace to lyx;
create temporary tablespace temp01 tempfile '/oracle/app/oracle/oradata/db3/temp01.dbf' size 20m;
alter database temporary tablespace temp01; alter tablespace add tempfile '/oracle/app/oracle/oradata/db3/temp01.dfb'; select file_name from dba_temp_files;
alter system set log_archive_dest_1='LOCATION=/oradata/arch';
shutdown immediate;
startup mount;
alter database archivelog;
alter database open;
archivelog log list;
alter system switch logfile;
select name from v$archived_log;
============================================================
测试hints:
sqlplus lyx/lyx;
SQL> set autotrace on SQL> select * from test;
U T ---------- ---------- LYX KKK LYX1 KKK
Execution Plan ---------------------------------------------------------- Plan hash value: 1357081020
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 2 | 16 | 3 (0)| 00:00:01 |
| 1 | TABLE ACCESS FULL| TEST | 2 | 16 | 3 (0)| 00:00:01 |
Note -----
- dynamic sampling used for this statement
Statistics ----------------------------------------------------------
316 recursive calls
0 db block gets
63 consistent gets
10 physical reads
0 redo size
501 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
6 sorts (memory)
0 sorts (disk)
2 rows processed
SQL> select * from test where t='KKK';
U T ---------- ---------- LYX KKK LYX1 KKK
Execution Plan ----------------------------------------------------------
Plan hash value: 1357081020
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 2 | 16 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| TEST | 2 | 16 | 3 (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - filter("T"='KKK')
Note ----- - dynamic sampling used for this statement
Statistics ----------------------------------------------------------
5 recursive calls
0 db block gets
16 consistent gets
0 physical reads
0 redo size
501 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
2 rows processed
SQL> select * from test where u='LYX1';
U T ---------- ---------- LYX1 KKK
Execution Plan ----------------------------------------------------------
Plan hash value: 4179085126
-------------------------------------------------------------------------------- ---------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| T ime |
-------------------------------------------------------------------------------- ---------
| 0 | SELECT STATEMENT | | 1 | 8 | 1 (0)| 0 0:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 8 | 1 (0)| 0 0:00:01 |
|* 2 | INDEX UNIQUE SCAN | PK_TEST_U | 1 | | 0 (0)| 0 0:00:01 |
-------------------------------------------------------------------------------- ---------
Predicate Information (identified by operation id):
2 - access("U"='LYX1')
Statistics ----------------------------------------------------------
1 recursive calls
0 db block gets
2 consistent gets
1 physical reads
0 redo size
461 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> select /*+FULL(TABLE)*/U FROM TEST WHERE U='LYX';
U ---------- LYX
Execution Plan ----------------------------------------------------------
Plan hash value: 3701598993
-------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1 | 4 | 0 (0)| 00:00:01 |
|* 1 | INDEX UNIQUE SCAN| PK_TEST_U | 1 | 4 | 0 (0)| 00:00:01 |
-------------------------------------------------------------------------------
Predicate Information (identified by operation id): ---------------------------------------------------
1 - access("U"='LYX')
Statistics ----------------------------------------------------------
1 recursive calls
0 db block gets
1 consistent gets
0 physical reads
0 redo size
405 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> select /*+FULL(TABLE)*/u,t from test where u='LYX1';
U T ---------- ---------- LYX1 KKK
Execution Plan ----------------------------------------------------------
Plan hash value: 4179085126
-------------------------------------------------------------------------------- ---------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| T ime |
-------------------------------------------------------------------------------- ---------
| 0 | SELECT STATEMENT | | 1 | 8 | 1 (0)| 0 0:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 8 | 1 (0)| 0 0:00:01 |
|* 2 | INDEX UNIQUE SCAN | PK_TEST_U | 1 | | 0 (0)| 0 0:00:01 |
-------------------------------------------------------------------------------- ---------
Predicate Information (identified by operation id): ---------------------------------------------------
2 - access("U"='LYX1')
Statistics ----------------------------------------------------------
1 recursive calls
0 db block gets
2 consistent gets
0 physical reads
0 redo size
461 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
另外，附上常见的hints命令：
1. /*+ALL_ROWS*/
表明对语句块选择基于开销的优化方法,并获得最佳吞吐量,使资源消耗最小化.
例如:
SELECT /*+ALL+_ROWS*/ EMP_NO,EMP_NAM,DAT_IN FROM BSEMPMS WHERE EMP_NO='SCOTT';
2. /*+FIRST_ROWS*/
表明对语句块选择基于开销的优化方法,并获得最佳响应时间,使资源消耗最小化.
例如:
SELECT /*+FIRST_ROWS*/ EMP_NO,EMP_NAM,DAT_IN FROM BSEMPMS WHERE EMP_NO='SCOTT';
3. /*+CHOOSE*/
表明如果数据字典中有访问表的统计信息,将基于开销的优化方法,并获得最佳的吞吐量;
表明如果数据字典中没有访问表的统计信息,将基于规则开销的优化方法;
例如:
SELECT /*+CHOOSE*/ EMP_NO,EMP_NAM,DAT_IN FROM BSEMPMS WHERE EMP_NO='SCOTT';
4. /*+RULE*/
表明对语句块选择基于规则的优化方法.
例如:
SELECT /*+ RULE */ EMP_NO,EMP_NAM,DAT_IN FROM BSEMPMS WHERE EMP_NO='SCOTT';
5. /*+FULL(TABLE)*/
表明对表选择全局扫描的方法.
例如:
SELECT /*+FULL(A)*/ EMP_NO,EMP_NAM FROM BSEMPMS A WHERE EMP_NO='SCOTT';
6. /*+ROWID(TABLE)*/
提示明确表明对指定表根据ROWID进行访问.
例如:
SELECT /*+ROWID(BSEMPMS)*/ * FROM BSEMPMS WHERE ROWID>='AAAAAAAAAAAAAA'
AND EMP_NO='SCOTT';
7. /*+CLUSTER(TABLE)*/
提示明确表明对指定表选择簇扫描的访问方法,它只对簇对象有效.
例如:
SELECT /*+CLUSTER */ BSEMPMS.EMP_NO,DPT_NO FROM BSEMPMS,BSDPTMS
WHERE DPT_NO='TEC304' AND BSEMPMS.DPT_NO=BSDPTMS.DPT_NO;
8. /*+INDEX(TABLE INDEX_NAME)*/
表明对表选择索引的扫描方法.
例如:
SELECT /*+INDEX(BSEMPMS SEX_INDEX) USE SEX_INDEX BECAUSE THERE ARE FEWMALE BSEMPMS */ FROM BSEMPMS WHERE SEX='M';
9. /*+INDEX_ASC(TABLE INDEX_NAME)*/
表明对表选择索引升序的扫描方法.
例如:
SELECT /*+INDEX_ASC(BSEMPMS PK_BSEMPMS) */ FROM BSEMPMS WHERE DPT_NO='SCOTT';
10. /*+INDEX_COMBINE*/
为指定表选择位图访问路经,如果INDEX_COMBINE中没有提供作为参数的索引,将选择出位图索引的布尔组合方式.
例如:
SELECT /*+INDEX_COMBINE(BSEMPMS SAL_BMI HIREDATE_BMI)*/ * FROM BSEMPMS
WHERE SAL<5000000 AND HIREDATE
11. /*+INDEX_JOIN(TABLE INDEX_NAME)*/
提示明确命令优化器使用索引作为访问路径.
例如:
SELECT /*+INDEX_JOIN(BSEMPMS SAL_HMI HIREDATE_BMI)*/ SAL,HIREDATE
FROM BSEMPMS WHERE SAL<60000;
12. /*+INDEX_DESC(TABLE INDEX_NAME)*/
表明对表选择索引降序的扫描方法.
例如:
SELECT /*+INDEX_DESC(BSEMPMS PK_BSEMPMS) */ FROM BSEMPMS WHERE DPT_NO='SCOTT';
13. /*+INDEX_FFS(TABLE INDEX_NAME)*/
对指定的表执行快速全索引扫描,而不是全表扫描的办法.
例如:
SELECT /*+INDEX_FFS(BSEMPMS IN_EMPNAM)*/ * FROM BSEMPMS WHERE DPT_NO='TEC305';
14. /*+ADD_EQUAL TABLE INDEX_NAM1,INDEX_NAM2,...*/
提示明确进行执行规划的选择,将几个单列索引的扫描合起来.
例如:
SELECT /*+INDEX_FFS(BSEMPMS IN_DPTNO,IN_EMPNO,IN_SEX)*/ * FROM BSEMPMS WHERE EMP_NO='SCOTT' AND DPT_NO='TDC306';
15. /*+USE_CONCAT*/
对查询中的WHERE后面的OR条件进行转换为UNION ALL的组合查询.
例如:
SELECT /*+USE_CONCAT*/ * FROM BSEMPMS WHERE DPT_NO='TDC506' AND SEX='M';
16. /*+NO_EXPAND*/
对于WHERE后面的OR 或者IN-LIST的查询语句,NO_EXPAND将阻止其基于优化器对其进行扩展.
例如:
SELECT /*+NO_EXPAND*/ * FROM BSEMPMS WHERE DPT_NO='TDC506' AND SEX='M';
17. /*+NOWRITE*/
禁止对查询块的查询重写操作.
18. /*+REWRITE*/
可以将视图作为参数.
19. /*+MERGE(TABLE)*/
能够对视图的各个查询进行相应的合并.
例如:
SELECT /*+MERGE(V) */ A.EMP_NO,A.EMP_NAM,B.DPT_NO FROM BSEMPMS A (SELET DPT_NO
,AVG(SAL) AS AVG_SAL FROM BSEMPMS B GROUP BY DPT_NO) V WHERE A.DPT_NO=V.DPT_NO
AND A.SAL>V.AVG_SAL;
20. /*+NO_MERGE(TABLE)*/
对于有可合并的视图不再合并.
例如:
SELECT /*+NO_MERGE(V) */ A.EMP_NO,A.EMP_NAM,B.DPT_NO FROM BSEMPMS A (SELECT DPT_NO,AVG(SAL) AS AVG_SAL FROM BSEMPMS B GROUP BY DPT_NO) V WHERE A.DPT_NO=V.DPT_NO AND A.SAL>V.AVG_SAL;
21. /*+ORDERED*/
根据表出现在FROM中的顺序,ORDERED使ORACLE依此顺序对其连接.
例如:
SELECT /*+ORDERED*/ A.COL1,B.COL2,C.COL3 FROM TABLE1 A,TABLE2 B,TABLE3 C WHERE A.COL1=B.COL1 AND B.COL1=C.COL1;
22. /*+USE_NL(TABLE)*/
将指定表与嵌套的连接的行源进行连接,并把指定表作为内部表.
例如:
SELECT /*+ORDERED USE_NL(BSEMPMS)*/ BSDPTMS.DPT_NO,BSEMPMS.EMP_NO,BSEMPMS.EMP_NAM FROM BSEMPMS,BSDPTMS WHERE BSEMPMS.DPT_NO=BSDPTMS.DPT_NO;
23. /*+USE_MERGE(TABLE)*/
将指定的表与其他行源通过合并排序连接方式连接起来.
例如:
SELECT /*+USE_MERGE(BSEMPMS,BSDPTMS)*/ * FROM BSEMPMS,BSDPTMS WHERE BSEMPMS.DPT_NO=BSDPTMS.DPT_NO;
24. /*+USE_HASH(TABLE)*/
将指定的表与其他行源通过哈希连接方式连接起来.
例如:
SELECT /*+USE_HASH(BSEMPMS,BSDPTMS)*/ * FROM BSEMPMS,BSDPTMS WHERE BSEMPMS.DPT_NO=BSDPTMS.DPT_NO;
25. /*+DRIVING_SITE(TABLE)*/
强制与ORACLE所选择的位置不同的表进行查询执行.
例如:
SELECT /*+DRIVING_SITE(DEPT)*/ * FROM BSEMPMS,DEPT@BSDPTMS WHERE BSEMPMS.DPT_NO=DEPT.DPT_NO;
26. /*+LEADING(TABLE)*/
将指定的表作为连接次序中的首表.
27. /*+CACHE(TABLE)*/
当进行全表扫描时,CACHE提示能够将表的检索块放置在缓冲区缓存中最近最少列表LRU的最近使用端
例如:
SELECT /*+FULL(BSEMPMS) CAHE(BSEMPMS) */ EMP_NAM FROM BSEMPMS;
28. /*+NOCACHE(TABLE)*/
当进行全表扫描时,CACHE提示能够将表的检索块放置在缓冲区缓存中最近最少列表LRU的最近使用端
例如:
SELECT /*+FULL(BSEMPMS) NOCAHE(BSEMPMS) */ EMP_NAM FROM BSEMPMS;
29. /*+APPEND*/
直接插入到表的最后,可以提高速度.
insert /*+append*/ into test1 select * from test4 ;
30. /*+NOAPPEND*/
通过在插入语句生存期内停止并行模式来启动常规插入.
insert /*+noappend*/ into test1 select * from test4 ;