??xml version="1.0" encoding="utf-8" standalone="yes"?>国产一区视频在线观看免费,国产99久久久国产精品免费看,日韩一级免费一区http://www.aygfsteel.com/xiekai-blog/category/18491.html北冥有鱼Q其名ؓ(f)鲌Ӏ鲲之大Q不知其几千里也。化而ؓ(f)鸟,其名为鹏。鹏之背Q不知其几千里也。怒而飞Q其D垂天之云。是鸟也Qvq则徙于南冥。南冥者,天池也? zh-cnTue, 31 Aug 2010 21:54:15 GMTTue, 31 Aug 2010 21:54:15 GMT60Oracle 的小技?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2010/08/31/330430.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Tue, 31 Aug 2010 07:58:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2010/08/31/330430.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/330430.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2010/08/31/330430.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/330430.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/330430.html</trackback:ping><description><![CDATA[■查询每张表有多个字段<br /> SELECT<br />     table_name,<br />     Count(*) As 列数<br /> FROM<br />     user_tab_columns<br /> GROUP BY<br />     table_name<br /> <img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/330430.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2010-08-31 15:58 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2010/08/31/330430.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>ORACLE的INSTANCE(实例)和SCHEMAQ方案、模式)http://www.aygfsteel.com/xiekai-blog/archive/2010/07/17/326417.html言w寸言w寸Sat, 17 Jul 2010 11:57:00 GMThttp://www.aygfsteel.com/xiekai-blog/archive/2010/07/17/326417.htmlhttp://www.aygfsteel.com/xiekai-blog/comments/326417.htmlhttp://www.aygfsteel.com/xiekai-blog/archive/2010/07/17/326417.html#Feedback0http://www.aygfsteel.com/xiekai-blog/comments/commentRss/326417.htmlhttp://www.aygfsteel.com/xiekai-blog/services/trackbacks/326417.html每一个运行的ORACLE数据库与一个ORACLE实例QINSTANCEQ相联系?br /> 一个ORACLE实例为存取和控制一数据库的软g机制?/span>每一ơ在数据库服务器上启动一数据库时Q称为系l全局区(SYSTEM
GLOBAL AREAQ的一内存区(USGAQ被分配Q有一个或多个ORACLEq程被启动。该SGA ?
ORACLEq程的结合称Z个ORACLE数据库实例?/span>一个实例的SGA和进Eؓ(f)理数据库数据、ؓ(f)该数据库一个或多个用户服务而工作?
ORACLE在内存存储下列信息:(x)
l 执行的程序代码?
l q接的会(x)话信?
l E序执行期间所需数据和共享的信息
l 存储在外存储上的~冲信息?
ORACLEh下列基本的内存结构:(x)
l 软g代码?
l pȝ全局?包括数据库缓冲存储区、日志缓冲区和共享池.
l E序全局?包括栈区和数据区.
l 排序?

软g代码?
用于存储正在执行的或可以执行的程序代码?
软g区是只读Q可安装成共享或非共享。ORACLEpȝE序是可׃n的,以致多个ORACLE用户可存取它Q而不需要在内存有多个副本。用L(fng)序可以共享也可以不共享?

pȝ全局?
Zl由O(jin)RACLE分配的共享的内存l构Q可包含一个数据库实例的数据或控制信息。如果多个用户同时连接到同一实例Ӟ在实例的SGA中数据可为多个用h׃nQ所以又UCؓ(f)׃n全局区。当实例起动ӞSGA的存储自动地被分配;当实例关闭时Q该存储被回收。所有连接到多进E数据库实例的全部用户可自动地被分配Q当实例关闭Ӟ该存储被回收。所有连接到多进E数据库实例的全部用户可使用其SGA中的信息Q但仅仅有几个进E可写入信息。在SGA中存储信息将内存划分成几个区Q数据库~冲存储区、日志缓冲区、共享池、请求和响应队列、数据字典存储区和其它各U信息?

E序全局?
PGA是一个内存区Q包含单个进E的数据和控制信息,所以又UCؓ(f)q程全局区(PROCESS GLOBAL AREAQ?

排序?
排序需要内?nobr style="color: #6600ff; border-bottom: #6600ff 1px dotted; background-color: transparent; text-decoration: underline" target="_blank">I间QORACLE利用该内存排序数据,q部分空间称为排序区。排序区存在于请求排序的用户q程的内存中Q该I间的大ؓ(f)适就排序数据量的大小Q可增长Q但受初始化参数SORT-AREA-SIZER所限制?

Ҏ(gu)也叫模式Q一个模?schema)为模式对?scehma object)的一个集合,每一个数据库用户对应一个模式?/span>模式对象为直接引用数据库数据的逻辑l构Q模式对象包含如表、视图、烦引、聚集、序列、同义词、数据库链、过E和包等l构。模式对象是逻辑数据存储l构。一个模式对象逻辑地存储在数据库的一个表I间中,每一个对象的数据物理地包含在表空间的一个或多个数据文g中?/p>

Q?/p>

服务器可用内存较?yu),采用多方案。多个SCHEMAQ方案、模式)

服务器可用内存充I采用多实例。多个INSTANCE(实例)



言w寸 2010-07-17 19:57 发表评论
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Oracle中sequence的用方?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2009/10/12/297904.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Mon, 12 Oct 2009 08:02:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2009/10/12/297904.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/297904.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2009/10/12/297904.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/297904.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/297904.html</trackback:ping><description><![CDATA[在Oracle数据库中Qsequence{同于序列号Q每ơ取的时候sequence?x)自动增加,一般会(x)作用于需要按序列h序的地方?br /> <br /> 1、Create Sequence<br /> (注释Q你需要有CREATE SEQUENCE或CREATE ANY SEQUENCE权限)<br /> CREATE SEQUENCE emp_sequence<br /> INCREMENT BY 1 —?每次加几?br /> START WITH 1 —??开始计?br /> NOMAXVALUE —?不设|最大?br /> NOCYCLE —?一直篏加,不@?br /> CACHE 10;<br /> - 假如指定CACHE|Oracle可以预先在内存里面攄一些sequenceQ这样存取的快些。cache里面的取完后QOracle自动再取一l到cache. 使用cache或许?x)蟩P 比如数据库突然不正常down?shutdown abort)Qcache中的sequence׃(x)丢失?所以可以在create sequence的时候用nocache防止q种情况?br /> <br /> 只要定义了emp_sequenceQ你可以用使CURRVALQNEXTVAL<br /> CURRVAL=q回 sequence的当前?br /> NEXTVAL=增加sequence的|然后q回 sequence ?br /> 例如Q?br /> emp_sequence.CURRVAL<br /> emp_sequence.NEXTVAL<br /> <br /> 可以使用sequence的地方:(x)<br /> 。不包含子查询、snapshot、VIEW?SELECT 语句<br /> 。INSERT语句的子查询?br /> 。INSERT语句的VALUES?br /> 。UPDATE ?SET?br /> 例:(x)<br /> INSERT INTO emp VALUES<br /> (empseq.nextval, 'LEWIS', 'CLERK',7902, SYSDATE, 1200, NULL, 20);<br /> SELECT empseq.currval FROM DUAL;<br /> <br /> 2、Alter Sequence<br /> 你需要有sequence的ownerQ或者拥有ALTER ANY SEQUENCE 权限才能改动sequence.<br /> 可以alter除start至以外的所有sequence参数。如果想要改变start|必须 drop sequence ?re-create .<br /> <br /> Alter sequenceCZQ?br /> <pre>ALTER SEQUENCE emp_sequence INCREMENT BY 10 MAXVALUE 10000 CYCLE -- ?0000后从头开?NOCACHE ;<br /> </pre> <img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/297904.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2009-10-12 16:02 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2009/10/12/297904.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>delete from tablea & truncate table tablea 的区?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287170.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Fri, 17 Jul 2009 07:26:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287170.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/287170.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287170.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/287170.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/287170.html</trackback:ping><description><![CDATA[相同?truncate和不带where子句的delete, 以及(qing)drop都会(x)删除表内的数?nbsp; <br /> 不同?  <br /> 1. truncate?delete只删除数据不删除表的l构(定义)  <br />      drop语句删除表的结构被依赖的约?constrain),触发?trigger),索引(index); 依赖于该表的存储q程/函数保?但是变ؓ(f)invalid状?  <br /> 2.delete语句是dml,q个操作?x)放到rollback segement?事务提交之后才生?如果有相应的trigger,执行的时候将被触?  <br />     truncate,drop是ddl, 操作立即生效,原数据不攑ֈrollback segment?不能回滚. 操作不触发trigger.  <br /> 3.速度,一般来? drop> truncate > delete<br /> 4.惛_除表,当然用drop。想保留表而将所有数据删? 如果和事务无?用truncate卛_. 如果和事务有?或者想触发trigger,q是用delete.  <br /> <img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/287170.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2009-07-17 15:26 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287170.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>Oracle的exp和imphttp://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287157.html言w寸言w寸Fri, 17 Jul 2009 07:05:00 GMThttp://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287157.htmlhttp://www.aygfsteel.com/xiekai-blog/comments/287157.htmlhttp://www.aygfsteel.com/xiekai-blog/archive/2009/07/17/287157.html#Feedback0http://www.aygfsteel.com/xiekai-blog/comments/commentRss/287157.htmlhttp://www.aygfsteel.com/xiekai-blog/services/trackbacks/287157.html 其实Q这是Oracle自带的两个工P在Oracle的安装目录的BIN目录下,可以看到exp.exe和imp.exe?br />
q行-->输入cmd-->q入DOS环境-->输入命o(h)Qexp 用户?密码@数据库名  file=xxx.dmp
可以实现数据库的导Z Q前提是要设|环境变量PATH=C:\oracle\product\10.2.0\client_1\binQ?br />
或者通过TeraTerm之类的Y件登录数据库服务器,d成功后运行命令:(x)exp 用户?密码  file=xxx.dmp

通过q个Ҏ(gu)Q一下子可以把数据库的表,视图Q触发器Q包{数据库对象全部导出成dmp文g?br /> 再通过imp命o(h)Q就可以实现数据库的转储?

言w寸 2009-07-17 15:05 发表评论
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Oracle SQL ?RANK & DENSE_RANK 的应?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2007/11/29/163961.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Thu, 29 Nov 2007 04:22:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2007/11/29/163961.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/163961.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2007/11/29/163961.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/163961.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/163961.html</trackback:ping><description><![CDATA[<p><span id="wmqeeuq" class="bold">Oracle中聚合函数RANK和DENSE_RANK的?</span><br /> <br /> 期末考试成W表(T_QMKSCJQ?br /> q度 班?nbsp;U目?nbsp;学生学号 成W<br /> 2000 001 0001 00001001 88<br /> 2000 001 0001 00001002 99<br /> 2000 001 0001 00001003 89<br /> 2000 001 0002 00001001 87<br /> 2000 001 0002 00001002 60<br /> 2000 001 0002 00001003 70<br /> 2000 002 0001 00002001 88<br /> 2000 002 0001 00002002 99<br /> 2000 002 0001 00002003 89<br /> 2000 002 0002 00002001 87<br /> 2000 002 0002 00002002 60<br /> 2000 002 0002 00002003 70<br />                         <br /> 2001 001 0001 01001001 88<br /> 2001 001 0001 01001002 99<br /> 2001 001 0001 01001003 89<br /> 2001 001 0002 01001001 87<br /> 2001 001 0002 01001002 60<br /> 2001 001 0002 01001003 70<br /> 2001 002 0001 01002001 88<br /> 2001 002 0001 01002002 99<br /> 2001 002 0001 01002003 89<br /> 2001 002 0002 01002001 87<br /> 2001 002 0002 01002002 60<br /> 2001 002 0002 01002003 70<br /> 2001 003 0003 01003001 87<br /> 2001 003 0003 01003002 60<br /> 2001 003 0003 01003003 70</p> <p>1Q选出各年度各班各科目第一名的学生的信息(q度Q班U号Q科目号Q成l,学号)</p> <p>select T.q度, T.班? T.U目? T.成WQT.学生学号Q?br />        dense_rank() over (partition by T.q度, T.班? T.U目?order by T.成W desc) T.排名<br /> from   T_QMKSCJ T<br /> where  T.排名 = '1'</p> <p><br /> 2Q选出各年度各班各科目第一名的学生的信息(q度Q班U名Q科目名Q成l,学号Q学生姓?</p> <p>select T.q度, T.班? T.U目? T.成WQT.学生学号QT.学生姓名Q?br />        dense_rank() over (partition by T.q度, T.班? T.U目?order by T.成W desc) T.排名<br /> from   <br />   (select <br />        A.q度, A.班? A.U目? A.成WQA.学生学号QB.班? C.学生姓名, D.U目?br />    from<br />        T_QMKSCJ A,<br />        T_班 B,<br />        T_学生 C,<br />        T_U目 D<br />    where  A.班?= B.班?br />      and  A.学生学号 = C.学生学号<br />      and  A.U目?= D.U目?br />   ) T<br /> where T.排名 = '1'</p> <p><br />  <br /> 3Q某q度某班U的某学生的某门U目的考试成W在其班排第几?</p> <p>q度 班?nbsp;U目?nbsp;学生学号 成W<br /> 2001 002 0001 01002003 89</p> <p>SELECT     <br />       RANK(2001,002,0001,89) WITHIN GROUP     <br />       (ORDER BY T.q度, T.班? T.U目? T.成W DESC) T.排名     <br /> FROM T_QMKSCJ T</p> <p>注意:<br /> Rank()里的参数必须为常?或常D辑ּ,里面参数的个?cd也要和order by后字D늚cd相对?</p> <img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/163961.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2007-11-29 12:22 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2007/11/29/163961.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>L解决CSE中不昄TimeStamp的问?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2007/10/25/155886.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Thu, 25 Oct 2007 08:09:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2007/10/25/155886.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/155886.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2007/10/25/155886.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/155886.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/155886.html</trackback:ping><description><![CDATA[以前用CSE查询数据库表Ӟl果中TimeStamp的字D|L昄为空Q不要以个字D中没有|很可能只是没有显C出来?br /> select timestamp from table<br /> where ....<br /> <br /> 其实只要加上to_char()命o(h)Q就可以让隐藏v来的数g乖显C出来?br /> select to_char(timestamp) from table <br /> where ....<br /> <br /> q一步,q可以控制显C的格式?br /> select <br />     to_char(timestamp, 'yyyy/mm/dd hh:mi:ss') <br /> from <br />     table<br /> where <br />     rownum < 'n'   --只显Ctable中前n-1条记录?- <img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/155886.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2007-10-25 16:09 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2007/10/25/155886.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>oracle SQL性能优化http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95241.html言w寸言w寸Mon, 22 Jan 2007 03:16:00 GMThttp://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95241.htmlhttp://www.aygfsteel.com/xiekai-blog/comments/95241.htmlhttp://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95241.html#Feedback0http://www.aygfsteel.com/xiekai-blog/comments/commentRss/95241.htmlhttp://www.aygfsteel.com/xiekai-blog/services/trackbacks/95241.html阅读全文

言w寸 2007-01-22 11:16 发表评论
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Oracle的WHERE语句中的索引的?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95240.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Mon, 22 Jan 2007 03:13:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95240.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/95240.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95240.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/95240.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/95240.html</trackback:ping><description><![CDATA[ <font color="#000000"> <span style="COLOR: blue">索引是表的一个概念部?/span> <span style="COLOR: blue">,</span> <span style="COLOR: blue">用来提高?gu)(g)索数据的效率Q?/span> <span style="COLOR: blue">ORACLE</span> <span style="COLOR: blue">使用了一个复杂的自^?/span> <span style="COLOR: blue">B-tree</span> <span style="COLOR: blue">l构</span> <span style="COLOR: blue">. </span> <span style="COLOR: blue">通常</span> <span style="COLOR: blue">,</span> <span style="COLOR: blue">通过索引查询数据比全表扫描要?/span> <span style="COLOR: blue">. </span> <span style="COLOR: blue">?/span> <span style="COLOR: blue">ORACLE</span> <span style="COLOR: blue">扑և执行查询?/span> <span style="COLOR: blue">Update</span> <span style="COLOR: blue">语句的最佌\径时</span> <span style="COLOR: blue">, ORACLE</span> <span style="COLOR: blue">优化器将使用索引?/span> </font> <br /> <font color="#000000">大部分的性能问题其实都是索引应用的问题,W(xu)here子句、Order By、Group By 都要用到索引?br />一般开发h员认为将索引建全了就可以下班回家了,实则q有颇多的思量和陷阱?/font> <br /> <br /> <strong>索引列上不要使用<font face="Microsoft Sans Serif" size="2">IS NULL ?IS NOT NULL<br /></font></strong> <div style="BORDER-RIGHT: #cccccc 1px solid; PADDING-RIGHT: 5px; BORDER-TOP: #cccccc 1px solid; PADDING-LEFT: 4px; FONT-SIZE: 13px; PADDING-BOTTOM: 4px; BORDER-LEFT: #cccccc 1px solid; WIDTH: 98%; WORD-BREAK: break-all; PADDING-TOP: 4px; BORDER-BOTTOM: #cccccc 1px solid; BACKGROUND-COLOR: #eeeeee"> <span style="COLOR: #000000">× SELECT Col FROM tbl WHERE col IS NULL</span> </div> <br /> <strong>索引列上不要使用函数<br /></strong> <div style="BORDER-RIGHT: #cccccc 1px solid; PADDING-RIGHT: 5px; BORDER-TOP: #cccccc 1px solid; PADDING-LEFT: 4px; FONT-SIZE: 13px; PADDING-BOTTOM: 4px; BORDER-LEFT: #cccccc 1px solid; WIDTH: 98%; WORD-BREAK: break-all; PADDING-TOP: 4px; BORDER-BOTTOM: #cccccc 1px solid; BACKGROUND-COLOR: #eeeeee"> <span style="COLOR: #000000">× SELECT Col FROM tbl WHERE substr(name</span> <span style="COLOR: #000000">,</span> <span style="COLOR: #000000"> </span> <span style="COLOR: #000000">1</span> <span style="COLOR: #000000">,</span> <span style="COLOR: #000000"> </span> <span style="COLOR: #000000">3</span> <span style="COLOR: #000000">) </span> <span style="COLOR: #000000">=</span> <span style="COLOR: #000000"> 'ABC'<br />○ SELECT Col FROM tbl WHERE name LIKE 'ABC%'<br /></span> </div> <font color="#0000ff">WHERE<span style="COLOR: blue">子句中,如果索引列是函数的一部分Q优化器不使用索引而用全表扫描.<br /></span></font> <br /> <strong>索引列上不要使用NOT</strong> <font size="3"> <span style="FONT-SIZE: 10pt; FONT-FAMILY: 'MS UI Gothic'; mso-bidi-font-size: 12.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Microsoft Sans Serif'; mso-hansi-font-family: 'Microsoft Sans Serif'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: JA; mso-bidi-language: AR-SA">Q?/span> <span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: 'Microsoft Sans Serif'; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 'MS UI Gothic'; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: JA; mso-bidi-language: AR-SA">!=</span> <span style="FONT-SIZE: 10pt; FONT-FAMILY: 'MS UI Gothic'; mso-bidi-font-size: 12.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Microsoft Sans Serif'; mso-hansi-font-family: 'Microsoft Sans Serif'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: JA; mso-bidi-language: AR-SA">?/span> <span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: 'Microsoft Sans Serif'; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 'MS UI Gothic'; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: JA; mso-bidi-language: AR-SA"><></span> <span style="FONT-SIZE: 10pt; FONT-FAMILY: 'MS UI Gothic'; mso-bidi-font-size: 12.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Microsoft Sans Serif'; mso-hansi-font-family: 'Microsoft Sans Serif'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: JA; mso-bidi-language: AR-SA">Q?br /></span> </font> <div style="BORDER-RIGHT: #cccccc 1px solid; PADDING-RIGHT: 5px; BORDER-TOP: #cccccc 1px solid; PADDING-LEFT: 4px; FONT-SIZE: 13px; PADDING-BOTTOM: 4px; BORDER-LEFT: #cccccc 1px solid; WIDTH: 98%; WORD-BREAK: break-all; PADDING-TOP: 4px; BORDER-BOTTOM: #cccccc 1px solid; BACKGROUND-COLOR: #eeeeee"> <span style="COLOR: #000000">× SELECT Col FROM tbl WHERE col !</span> <span style="COLOR: #000000">=</span> <span style="COLOR: #000000"> </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> <br />○ SELECT Col FROM tbl WHERE col > </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> OR col < </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> <br /> </span> </div> <p align="left"> <font color="#0000ff"> <span style="COLOR: blue">C</span> <span style="COLOR: blue">, </span> <span style="COLOR: blue">索引只能告诉你什么存在于表中</span> <span style="COLOR: blue">, </span> <span style="COLOR: blue">而不能告诉你什么不存在于表?/span> <span style="COLOR: blue">.</span> <span style="COLOR: purple"> </span>要避免在索引列上使用<span style="COLOR: blue">NOT, NOT</span><span style="COLOR: blue">?x)生在和在索引列上使用函数相同?/span><span style="COLOR: blue">影响</span><span style="COLOR: blue">. </span><span style="COLOR: blue">?/span><span style="COLOR: blue">ORACLE?/span><span style="COLOR: blue">遇到</span><span style="COLOR: blue">”NOT,</span><span style="COLOR: blue">他就?x)停止用烦引{而执行全表扫描?br /></span></font> <br /> <strong>索引列上不要q行计算</strong> <span style="FONT-SIZE: 8pt; FONT-FAMILY: 'MS UI Gothic'; mso-ascii-font-family: 'Microsoft Sans Serif'; mso-hansi-font-family: 'Microsoft Sans Serif'"> </span> </p> <div style="BORDER-RIGHT: #cccccc 1px solid; PADDING-RIGHT: 5px; BORDER-TOP: #cccccc 1px solid; PADDING-LEFT: 4px; FONT-SIZE: 13px; PADDING-BOTTOM: 4px; BORDER-LEFT: #cccccc 1px solid; WIDTH: 98%; WORD-BREAK: break-all; PADDING-TOP: 4px; BORDER-BOTTOM: #cccccc 1px solid; BACKGROUND-COLOR: #eeeeee"> <span style="COLOR: #000000">× SELECT Col FROM tbl WHERE col / </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> > </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> <br />○ SELECT Col FROM tbl WHERE col > </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> * </span> <span style="COLOR: #000000">10</span> <span style="COLOR: #000000"> <br /> </span> </div> <font color="#0000ff">q是最最普遍的失效陷阱,比如where trunc(order_date)=trunc(sysdate), i+2>4。烦引失效的原因也简单,索引是针对原值徏的二叉树(wi)Q你列?3/4+2折腾一番后Q原来的二叉?wi)当然就用不上了?br /></font> <br /> <br /> <br /> <p class="MsoNormal" style="MARGIN: 0mm 0mm 0pt 21pt; TEXT-INDENT: -21pt; mso-list: l0 level1 lfo1; tab-stops: list 21.0pt"> <span lang="EN-US" style="FONT-FAMILY: Wingdings; mso-bidi-font-size: 10.0pt; mso-fareast-font-family: Wingdings; mso-bidi-font-family: Wingdings"> <span style="mso-list: Ignore"> <span style="FONT: 7pt 'Times New Roman'"> <font face="Wingdings" size="2"> <br /> </font> </span> </span> </span> </p> <p> <br /> </p> <img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/95240.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2007-01-22 11:13 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95240.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>Oracle中DECODE的?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95221.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Mon, 22 Jan 2007 01:57:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95221.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/95221.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95221.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/95221.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/95221.html</trackback:ping><description><![CDATA[含义解释Q?br /><br /><font color="#0000ff"><font color="#000000">    </font><strong><u>DECODE</u></strong></font>(条g,?,译?,?,译?,...值n,译值n,~省?<br /><br />    该函数的含义如下Q?br /><br />IF 条g=? THEN<br />    RETURN(译?)<br />ELSIF 条g=? THEN<br />    RETURN(译?)<br />    ......<br />ELSIF 条g=值n THEN<br />    RETURN(译值n)<br />ELSE<br />    RETURN(~省?<br />END IF<br /><img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/95221.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2007-01-22 09:57 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2007/01/22/95221.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>SQL文中关于UNION和左q接的?/title><link>http://www.aygfsteel.com/xiekai-blog/archive/2006/12/18/88472.html</link><dc:creator>言w寸</dc:creator><author>言w寸</author><pubDate>Mon, 18 Dec 2006 03:44:00 GMT</pubDate><guid>http://www.aygfsteel.com/xiekai-blog/archive/2006/12/18/88472.html</guid><wfw:comment>http://www.aygfsteel.com/xiekai-blog/comments/88472.html</wfw:comment><comments>http://www.aygfsteel.com/xiekai-blog/archive/2006/12/18/88472.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/xiekai-blog/comments/commentRss/88472.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/xiekai-blog/services/trackbacks/88472.html</trackback:ping><description><![CDATA[     摘要: 最q一直在做一个项目,很久没来q里写东西了。项目刚完成W一期,W二期就接踵而至了。在一期中Q我发现自己对SQL文还有不知识的I白点,比如对于UNION和左q接的用,下面p斚w做些W记Q与大家׃n。■目中用的DB是Oracle。■例一Q注意UNION的用。  ★详l式样中的SQL文(部分Q:(x)取得項目  省略選択条g  請求D高Q今回締日 Q 画面Q「締日」結合条件  得意先.得意先コヹ{...  <a href='http://www.aygfsteel.com/xiekai-blog/archive/2006/12/18/88472.html'>阅读全文</a><img src ="http://www.aygfsteel.com/xiekai-blog/aggbug/88472.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/xiekai-blog/" target="_blank">言w寸</a> 2006-12-18 11:44 <a href="http://www.aygfsteel.com/xiekai-blog/archive/2006/12/18/88472.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item></channel></rss> <footer> <div class="friendship-link"> <a href="http://www.aygfsteel.com/" title="狠狠久久亚洲欧美专区_中文字幕亚洲综合久久202_国产精品亚洲第五区在线_日本免费网站视频">狠狠久久亚洲欧美专区_中文字幕亚洲综合久久202_国产精品亚洲第五区在线_日本免费网站视频</a> </div> </footer> վ֩ģ壺 <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">dz</a>| <a href="http://" target="_blank">γ</a>| <a href="http://" target="_blank">«ɽ</a>| <a href="http://" target="_blank">̴</a>| <a href="http://" target="_blank">¡</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">μԴ</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">ͺ</a>| <a href="http://" target="_blank">ɽ</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">ɽ</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">Զ</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">˳</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">ɽ</a>| <a href="http://" target="_blank">ɽ</a>| <a href="http://" target="_blank">ǿ</a>| <a href="http://" target="_blank">ʳ</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">׷</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">ҵ</a>| <a href="http://" target="_blank">»</a>| <a href="http://" target="_blank">֣</a>| <a href="http://" target="_blank">ƽ</a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank"></a>| <a href="http://" target="_blank">㰲</a>| <script> (function(){ var bp = document.createElement('script'); var curProtocol = window.location.protocol.split(':')[0]; if (curProtocol === 'https') { bp.src = 'https://zz.bdstatic.com/linksubmit/push.js'; } else { bp.src = 'http://push.zhanzhang.baidu.com/push.js'; } var s = document.getElementsByTagName("script")[0]; s.parentNode.insertBefore(bp, s); })(); </script> </body>