�??xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/"><channel><title>&#27431;&#32654;&#19987;&#21306;&#31532;&#19968;&#39029;&#44;&#36229;&#30896;&#97;&#8564;&#20154;&#20154;&#20570;&#20154;&#20154;&#29245;&#27431;&#32654;&#44;&#25104;&#20154;&#104;&#35270;&#39057;&#22312;&#32447;</title><link>http://www.aygfsteel.com/swingboat/category/6384.html</link><description>&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;----只要路选对了，��׃��怕有多远�Q?/description><language>zh-cn</language><lastBuildDate>Sat, 26 May 2007 11:52:22 GMT</lastBuildDate><pubDate>Sat, 26 May 2007 11:52:22 GMT</pubDate><ttl>60</ttl><item><title>有关�?”和“_”的search�?/title><link>http://www.aygfsteel.com/swingboat/archive/2007/05/24/119848.html</link><dc:creator>swingboat</dc:creator><author>swingboat</author><pubDate>Thu, 24 May 2007 15:28:00 GMT</pubDate><guid>http://www.aygfsteel.com/swingboat/archive/2007/05/24/119848.html</guid><wfw:comment>http://www.aygfsteel.com/swingboat/comments/119848.html</wfw:comment><comments>http://www.aygfsteel.com/swingboat/archive/2007/05/24/119848.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/swingboat/comments/commentRss/119848.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/swingboat/services/trackbacks/119848.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 今天下午QA�l�我报了一个bug�Q�说输入&#8220;f+f&#8221;或�?#8220;f_f&#8221;能够搜烦�?#8220;f f&#8221;的结果。看着�q�bug的描�q�ͼ�心里�q�想着怎么�?x��)呢�Q�模�p�查询也不会(x��)出现�q�样的结果啊�Q�赶紧自��p���?#8220;f+f&#8221;�?#8220;f_f&#8221;验证下，�l�果两次都输��Z��&#8220;f f&#8221;。由于查询的条�g是通过URL后的参数输入的，当我输入&#8220;f+f&#8221;�Ӟ��发现参数传入到服务端后变成了&#8220;f f&#8221;了，如果是这��P��那search的结果是正确的。但��Z��么输入的参数&#8220;f+f&#8221;怎么�?x��)变成�?#8220;f f&#8221;呢？而且在输入参数都通过escape�q�行�~�码了。于是上�|�google了一下，发现escape函数是不�?x��)�?#8220;+&#8221;�q�行�~�码的，但请求时�Q�web服务器会(x��)�q���o(h��)�?#8220;+&#8221;�q�个字符。所以我们必���L��工对&#8220;+&#8221;�q�行�~�码�Q�把所有的&#8220;+&#8221;都改变�ؓ(f��)&#8220;%2b&#8221;。修改代码测试，再次输入&#8220;f+f&#8221;�Q�结果不能搜索出&#8220;f f&#8221;的结果了�?br>而对输入&#8220;f_f&#8221;搜烦�?#8220;f f&#8221;的结果，主要原因是这个是模糊查询的一�U��?#8220;f_f&#8221;表示搜烦出含有两�?#8220;f&#8221;字符而且中间有一个字�W�分隔的�Q?#8220;f&nbsp; f&#8221;正好满���q�个条�g�Q�于是被搜烦��Z���?br>
<img src ="http://www.aygfsteel.com/swingboat/aggbug/119848.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/swingboat/" target="_blank">swingboat</a> 2007-05-24 23:28 <a href="http://www.aygfsteel.com/swingboat/archive/2007/05/24/119848.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>利用sql语句实现的几个功�?</title><link>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25668.html</link><dc:creator>swingboat</dc:creator><author>swingboat</author><pubDate>Wed, 28 Dec 2005 01:23:00 GMT</pubDate><guid>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25668.html</guid><wfw:comment>http://www.aygfsteel.com/swingboat/comments/25668.html</wfw:comment><comments>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25668.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/swingboat/comments/commentRss/25668.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/swingboat/services/trackbacks/25668.html</trackback:ping><description><![CDATA[<div   id="wmqeeuq"   class=postText>
<P>1、SQL 语句中，union的���? <BR>&nbsp;&nbsp; Table a:&nbsp;&nbsp;&nbsp; field1,field2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Table b:&nbsp;&nbsp; field1,field2 <BR>&nbsp;&nbsp; data:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; data:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2,&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp; <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2,&nbsp;&nbsp;&nbsp;&nbsp; 3 <BR>&nbsp;&nbsp; sql:&nbsp; select filed1 from a union select field1 from b <BR>&nbsp;&nbsp; data: field1 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2 <BR>&nbsp;&nbsp; sql:&nbsp; select filed1,field2 from a union select field1,field2 from b <BR>&nbsp;&nbsp; data: field1,field2 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3&nbsp; <BR>2、table1�?j��ng)id�Q�int�Q�charge�Q�int�Q�fk�Q�int�?<BR>&nbsp;&nbsp; table2�?j��ng)id�Q�int�Q�charge�Q�int�?<BR>&nbsp;&nbsp; 修改table2�Q���charge�{�于table1中相应值的�?<BR>&nbsp;&nbsp; sql�Q�update a set a.charge=b.totalcharge <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; from (select id,sum(charge) totalcharge from table1 group by id)&nbsp; b,table2 a <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; where a.id=b.id <BR>3、出发点&nbsp;&nbsp; 目的�?nbsp;&nbsp;&nbsp;&nbsp; 路程 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; C <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; D <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; E <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; F <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; C&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; G <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; C&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 用sql语句计算出所有从A出发所能到辄���目的圎ͼ�包括间接的�?<BR>&nbsp;&nbsp; sql�Q�select distinic 目的�?from �?<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; where 出发�?in ( <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; select distinic 目的�?from&nbsp; �?<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; where 出发�?'A' union select 'A') <BR>&nbsp;&nbsp; 说明�Q�上面的�Ҏ(gu��)��只��用一�U�嵌套。可以满���x��题的需求�?<BR>4、表t1 <BR>&nbsp;&nbsp;&nbsp;&nbsp; year&nbsp;&nbsp; quarter&nbsp;&nbsp; num <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2001&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3.4 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2001&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5.12 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2001&nbsp;&nbsp;&nbsp;&nbsp; 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 6.13 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2001&nbsp;&nbsp;&nbsp;&nbsp; 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8.14 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2002&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5.21 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2002&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4.22 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2002&nbsp;&nbsp;&nbsp;&nbsp; 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 6.23 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2002&nbsp;&nbsp;&nbsp;&nbsp; 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4.24 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 用sql语句获取下面的数�?<BR>&nbsp;&nbsp;&nbsp;&nbsp; 2001&nbsp; 3.4&nbsp; 5.12&nbsp; 6.13&nbsp; 8.14 <BR>&nbsp;&nbsp;&nbsp;&nbsp; 2002&nbsp; 5.21&nbsp; 4.22&nbsp; 6.23&nbsp; 4.24 </P>
<P>&nbsp;&nbsp; sql�Q�select [year],avg(case[quarter] when '1' then num) as 'quarter1', <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; avg(case[quarter] when '2' then num) as 'quarter2', <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; avg(case[quarter] when '3' then num) as 'quarter3', <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; avg(case[quarter] when '4' then num) as 'quarter4' <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; from t1 group by year <BR></P></DIV><img src ="http://www.aygfsteel.com/swingboat/aggbug/25668.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/swingboat/" target="_blank">swingboat</a> 2005-12-28 09:23 <a href="http://www.aygfsteel.com/swingboat/archive/2005/12/28/25668.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>Mysql 的中��q��问题 </title><link>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25669.html</link><dc:creator>swingboat</dc:creator><author>swingboat</author><pubDate>Wed, 28 Dec 2005 01:23:00 GMT</pubDate><guid>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25669.html</guid><wfw:comment>http://www.aygfsteel.com/swingboat/comments/25669.html</wfw:comment><comments>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25669.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/swingboat/comments/commentRss/25669.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/swingboat/services/trackbacks/25669.html</trackback:ping><description><![CDATA[环境�Q�winxp sp2�Q�jboss-3.2.3�Q�mysql 4.1 <BR>现象�Q�启动jboss�Q�浏览网��，能够从数据库中读出数据，但是所有中文数据都是“？�?<BR>原因�Q�可能有两种 <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1、mysql的确省字�W�集讄���的不是gb <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2、mysql-connector�Q�mysql官方提供的jdbc驱动�E�序�Q�有问题 <BR><BR>解决�Q?<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �W�一�U�情况：(x��)修改my.ini文�g。my.ini可能存在�pȝ��目录下（c:\windows�Q�和mysql所安装的目录下�Q�C:\Program Files\mysql\MySQL Server 4.1�Q�。打开my.ini文�g�Q�找到[mysqld]块。把default-character讄���为gbk�Q�如果没有找到则��d��即default-character-set=gbk�?重启mysql�Q�问题解冟�?<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;�W�二�U�情况：(x��)到mysql的官方网站下载最新的jdbc驱动�E�序。www.mysql.org <img src ="http://www.aygfsteel.com/swingboat/aggbug/25669.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/swingboat/" target="_blank">swingboat</a> 2005-12-28 09:23 <a href="http://www.aygfsteel.com/swingboat/archive/2005/12/28/25669.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>Oracle的几个��用问�?</title><link>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25667.html</link><dc:creator>swingboat</dc:creator><author>swingboat</author><pubDate>Wed, 28 Dec 2005 01:22:00 GMT</pubDate><guid>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25667.html</guid><wfw:comment>http://www.aygfsteel.com/swingboat/comments/25667.html</wfw:comment><comments>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25667.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/swingboat/comments/commentRss/25667.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/swingboat/services/trackbacks/25667.html</trackback:ping><description><![CDATA[1、在Windows的服务中“OracleServiceWINSOM”服务的状态�ؓ(f��)“启动”，所能执行的��d��也都是灰色的。Oracle没有正常的启动�?<BR>&nbsp;&nbsp; 解决�Q�run�Q�cmd <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; svrmgrl <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; connect internal/oracle <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; shutdown immediate <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; startup <BR>2、导入，导出数据 <BR>&nbsp;&nbsp; a、删除一个用��P��(x��) <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; drop user smartweb CASCADE <BR>&nbsp;&nbsp; b、创��Z��个用��P��(x��) <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; create user smartweb identified by smartweb <BR>&nbsp;&nbsp; c、给用户赋予权限�Q?<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; grant connect to smartweb <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; grant resource to smartweb <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; grant create session to smartweb <BR>&nbsp;&nbsp; d、连接：(x��) <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; conn smartweb/smartweb <BR>&nbsp;&nbsp; e、导入：(x��) <BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; imp <BR>3、查看oracle的版�?<BR>&nbsp;&nbsp; select * from v$version <BR>4、修改oracle中的Oracle Servlet Engine�Q�OSE�Q�所占的8080端口�Q�TNSLSNR.exe�Q��?<BR>&nbsp;&nbsp; 安装Oracle 9i�?080端口被OSE占用�Q�即tnslsnr.exe�q�程所占用。清除此端口�Ҏ(gu��)���Q?<BR>&nbsp;&nbsp; cd $ORACLE_HOME/jis/install <BR>&nbsp;&nbsp; sess_sh -u sys/change_on_install -role SYSDBA -s jdbc:oracle:oci8:@yhp <BR>&nbsp;&nbsp; <A href="mailto:$@serverendp.ssh"><FONT color=#000080>$@serverendp.ssh</FONT></A> <BR>&nbsp;&nbsp; $exit <BR>5、imp�Ӟ��出现的错误：(x��)不支持要求的字符集�{换（从类�?50�?52�Q?<BR>&nbsp;&nbsp; 使用函数NLS_CHARSET_NAME卛_��获得该字�W�集�Q?<BR>&nbsp;&nbsp; SQL&gt; select nls_charset_name(1) from dual; <BR>NLS_CHARSET_NAME(1) <BR>------------------- <BR>US7ASCII <BR>可以知道该dmp文�g的字�W�集为US7ASCII�Q�如果需要把该dmp文�g的字�W�集换成ZHS16GBK�Q�则需要用NLS_CHARSET_ID获取该字�W�集的编��P��(x��) <BR>SQL&gt; select nls_charset_id('zhs16gbk') from dual; <BR>NLS_CHARSET_ID('ZHS16GBK') <BR>-------------------------- <BR>852 <BR>�?52换成16�q�制敎ͼ��?54�Q�把2�?字节�?0 01换成03 54�Q�即完成了把该dmp文�g字符集从us7ascii到zhs16gbk的�{化，�q�样�Q�再把该dmp文�g导入到zhs16gbk字符集的数据库就可以了。（注意�Q�十�q�制��C��十六�q�制之间的�{换，��x��白其中的道理�Q?img src ="http://www.aygfsteel.com/swingboat/aggbug/25667.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/swingboat/" target="_blank">swingboat</a> 2005-12-28 09:22 <a href="http://www.aygfsteel.com/swingboat/archive/2005/12/28/25667.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>ORACLE SQL语句优化技术分�?</title><link>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25659.html</link><dc:creator>swingboat</dc:creator><author>swingboat</author><pubDate>Wed, 28 Dec 2005 01:19:00 GMT</pubDate><guid>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25659.html</guid><wfw:comment>http://www.aygfsteel.com/swingboat/comments/25659.html</wfw:comment><comments>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25659.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/swingboat/comments/commentRss/25659.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/swingboat/services/trackbacks/25659.html</trackback:ping><description><![CDATA[<STRONG>IN 操作�W?/STRONG>
<P>&nbsp;&nbsp;&nbsp;&nbsp;用IN写出来的SQL的优�Ҏ(gu��)��比较�Ҏ(gu��)��写及(qi��ng)清晰易懂�Q�这比较适合��C��软�g开发的风格�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;但是用IN的SQL性能��L��比较低的�Q�从ORACLE执行的步骤来分析用IN的SQL与不用IN的SQL有以下区别：(x��)</P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;ORACLE试图���其转换成多个表的连接，如果转换不成功则先执行IN里面的子查询�Q�再查询外层的表记录�Q�如果�{换成功则直接采用多个表的�q�接方式查询。由此可见用IN的SQL臛_��多了一个�{换的�q�程。一般的SQL都可以�{换成功，但对于含有分�l�统计等斚w��的SQL��׃��能�{换了�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;推荐�Ҏ(gu��)���Q�在业务密集的SQL当中���量不采用IN操作�W��?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;<B>NOT IN</B><B>操作�W?/B></P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;此操作是强列推荐不��用的�Q�因为它不能应用表的索引�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;推荐�Ҏ(gu��)���Q�用NOT EXISTS 或（外连�?判断为空�Q�方案代�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;<B>&lt;&gt; </B><B>操作�W�（不等于）</B></P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;不等于操作符是永�q�不�?x��)用到烦引的�Q�因此对它的处理只会(x��)产生全表扫描�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;推荐�Ҏ(gu��)���Q�用其它相同功能的操作运���代替，�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;a&lt;&gt;0 改�ؓ(f��) a&gt;0 or a&lt;0</P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;a&lt;&gt;’�?改�ؓ(f��) a&gt;’�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;<B>IS NULL </B><B>或IS NOT NULL</B><B>操作�Q�判断字�D�|��否�ؓ(f��)�I�）</B></P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;判断字段是否为空一般是不会(x��)应用索引的，因�ؓ(f��)B�?w��i)烦引是不烦引空值的�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;推荐�Ҏ(gu��)���Q?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;用其它相同功能的操作�q�算代替�Q�如</P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;a is not null 改�ؓ(f��) a&gt;0 或a&gt;’’等�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;不允许字�D��ؓ(f��)�I�，而用一个缺省��g��替空��|��如业扩申请中状态字�D�不允许为空�Q�缺省�ؓ(f��)甌����?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;建立位图索引�Q�有分区的表不能建，位图索引比较难控�Ӟ��如字�D�值太多烦引会(x��)使性能下降�Q�多人更新操作会(x��)增加数据块锁的现象）</P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;<B>&gt; </B><B>�?&lt; </B><B>操作�W�（大于或小于操作符�Q?/B></P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;大于或小于操作符一般情况下是不用调整的�Q�因为它有烦引就�?x��)采用烦引查找，但有的情况下可以对它�q�行优化�Q�如一个表�?00万记录，一个数值型字段A(ch��)�Q?0万记录的A=0�Q?0万记录的A=1�Q?9万记录的A=2�Q?万记录的A=3。那么执行A&gt;2与A&gt;=3的效果就有很大的区别了，因�ؓ(f��)A&gt;2时ORACLE�?x��)先扑և��?的记录烦引再�q�行比较�Q�而A&gt;=3时ORACLE则直接找�?3的记录烦引�?/P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;<B>LIKE</B><B>操作�W?/B></P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;LIKE操作�W�可以应用通配�W�查询，里面的通配�W�组合可能达到几乎是��L��的查询，但是如果用得不好则会(x��)产生性能上的问题�Q�如LIKE �?5400%�?�q�种查询不会(x��)引用索引�Q�而LIKE ‘X5400%’则�?x��)引用范围烦引。一个实际例子：(x��)用YW_YHJBQK表中营业�~�号后面的户标识号可来查询营业编�?YY_BH LIKE �?5400%�?�q�个条�g�?x��)��生全表扫描，如果��?gu��)��YY_BH LIKE ’X5400%�?OR YY_BH LIKE ’B5400%�?则会(x��)利用YY_BH的烦引进行两个范围的查询�Q�性能肯定大大提高�?/P><img src ="http://www.aygfsteel.com/swingboat/aggbug/25659.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/swingboat/" target="_blank">swingboat</a> 2005-12-28 09:19 <a href="http://www.aygfsteel.com/swingboat/archive/2005/12/28/25659.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>在Oracle中，快速获取一个部门以�?qi��ng)它下面所有的子部门的�Ҏ(gu��)���?</title><link>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25644.html</link><dc:creator>swingboat</dc:creator><author>swingboat</author><pubDate>Wed, 28 Dec 2005 01:01:00 GMT</pubDate><guid>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25644.html</guid><wfw:comment>http://www.aygfsteel.com/swingboat/comments/25644.html</wfw:comment><comments>http://www.aygfsteel.com/swingboat/archive/2005/12/28/25644.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/swingboat/comments/commentRss/25644.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/swingboat/services/trackbacks/25644.html</trackback:ping><description><![CDATA[<P>有一个部门表�Q�T_Department�Q�：(x��)<BR>T_Department�Q?BR>&nbsp;&nbsp;&nbsp;&nbsp; ID �Q�varchar2�Q?5)<BR>&nbsp;&nbsp;&nbsp;&nbsp; Name�Q�varchar2�Q?00)<BR>&nbsp;&nbsp;&nbsp;&nbsp; SuperiorID�Q�varchar2�Q?5�Q?BR>&nbsp;&nbsp;&nbsp;&nbsp; SuperiorName�Q�varchar2�Q?00)<BR>&nbsp;&nbsp;&nbsp;&nbsp; Remark�Q�varchar2�Q?000)</P>
<P><BR>�Ҏ(gu��)��一个部门的ID�Q�获取该部门下所有的子部�?例如部门的ID为“D”：(x��)<BR>select * from T_Department<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Start with&nbsp; ID='D'<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Connect by&nbsp; prior&nbsp; ID=SuperiorID</P><img src ="http://www.aygfsteel.com/swingboat/aggbug/25644.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/swingboat/" target="_blank">swingboat</a> 2005-12-28 09:01 <a href="http://www.aygfsteel.com/swingboat/archive/2005/12/28/25644.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item></channel></rss>                                                                                               <footer>
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