�??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>&#x65E5;&#x672C;&#x89C6;&#x9891;&#x4E00;&#x533A;&#x5728;&#x7EBF;&#x89C2;&#x770B;&#x0D;&#x2C;&#x4E9A;&#x6D32;&#x4EBA;&#x4F53;&#x4E00;&#x533A;&#x2C;&#x9752;&#x9752;&#x9752;&#x514D;&#x8D39;&#x89C6;&#x9891;&#x5728;&#x7EBF;&#x32;</title><link>http://www.aygfsteel.com/qbna350816/category/55123.html</link><description>201103</description><language>zh-cn</language><lastBuildDate>Fri, 23 Sep 2016 16:36:32 GMT</lastBuildDate><pubDate>Fri, 23 Sep 2016 16:36:32 GMT</pubDate><ttl>60</ttl><item><title>MySQL事务隔离�U�别详解</title><link>http://www.aygfsteel.com/qbna350816/archive/2016/09/24/431834.html</link><dc:creator>胡小�?/dc:creator><author>胡小�?/author><pubDate>Fri, 23 Sep 2016 16:06:00 GMT</pubDate><guid>http://www.aygfsteel.com/qbna350816/archive/2016/09/24/431834.html</guid><wfw:comment>http://www.aygfsteel.com/qbna350816/comments/431834.html</wfw:comment><comments>http://www.aygfsteel.com/qbna350816/archive/2016/09/24/431834.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.aygfsteel.com/qbna350816/comments/commentRss/431834.html</wfw:commentRss><trackback:ping>http://www.aygfsteel.com/qbna350816/services/trackbacks/431834.html</trackback:ping><description><![CDATA[<p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">SQL标准定义�?�c�隔��ȝ�别，包括�?ji��n)一些具体规则，用来限定事务内外的哪些改变是可见的，哪些是不可见的。低�U�别的隔��ȝ�一般支持更高的�q�发处理�Q��ƈ拥有更低的系�l�开销�?br /><strong>Read Uncommitted�Q�读取未提交内容�Q?/strong></span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 在该隔离�U�别�Q�所有事务都可以看到其他未提交事务的执行�l�果。本隔离�U�别很少用于实际应用�Q�因为它的性能也不比其他��别好多少。读取未提交的数据，也被�U�C�������读（Dirty Read�Q��?br /><strong>Read Committed�Q�读取提交内容）(j��)</strong></span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �q�是大多数数据库�pȝ��的默认隔��ȝ�别（但不是MySQL默认的）(j��)。它满���?ji��n)隔��ȝ�����单定义：(x��)一个事务只能看见已�l�提交事务所做的改变。这�U�隔��ȝ��?也支持所谓的不可重复读（Nonrepeatable Read�Q�，因�ؓ(f��)同一事务的其他实例在该实例处理其间可能会(x��)有新的commit�Q�所以同一select可能�q�回不同�l�果�?br /><strong>Repeatable Read�Q�可重读�Q?/strong></span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �q�是MySQL的默认事务隔��ȝ�别，它确保同一事务的多个实例在�q�发��d��数据�Ӟ���?x��)看到同��L(f��ng)��数据行。不�q�理��Z���Q�这�?x��)导致另一个棘手的问题�Q����?�Q�Phantom Read�Q�。简单的��_(d��)���q�读指当用户��d��某一范围的数据行�Ӟ��另一个事务又在该范围内插入了(ji��n)新行�Q�当用户再读取该范围的数据行�Ӟ���?x��)发现有新�?#8220;�q�d��(ji��ng)&#8221; 行。InnoDB和Falcon存储引擎通过多版本�ƈ发控�Ӟ��MVCC�Q�Multiversion Concurrency Control�Q�机制解决了(ji��n)该问题�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;"><strong>Serializable�Q�可串行化）(j��)</strong>&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �q�是最高的隔离�U�别�Q�它通过强制事务排序�Q���之不可能�怺�冲突�Q�从而解军_��读问题。简�a�之，它是在每个读的数据行上加上共享锁。在�q�个�U�别�Q�可能导致大量的���时现象和锁竞争�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="font-size: medium;">�q�四�U�隔��ȝ�别采取不同的锁类型来实现�Q�若��d��的是同一个数据的话，���容易发生问题。例如：(x��)</span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="font-size: medium;">&nbsp;&nbsp; 脏读(Drity Read)�Q�某个事务已更新一份数据，另一个事务在此时��d���?ji��n)同一份数据，�׃��某些原因�Q�前一个RollBack�?ji��n)操作，则后一个事务所��d��的数据就�?x��)是不正���的�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="font-size: medium;">不可重复�?Non-repeatable read):在一个事务的两次查询之中数据不一��_(d��)���q�可能是两次查询�q�程中间插入�?ji��n)一个事务更新的原有的数据�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �q�读(Phantom Read):在一个事务的两次查询中数据笔��C��一��_(d��)��例如有一个事务查询了(ji��n)几列(Row)数据�Q�而另一个事务却在此时插入了(ji��n)新的几列数据�Q�先前的事务在接下来的查询中�Q�就�?x��)发现有几列数据是它先前所没有的�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 在MySQL中，实现�?ji��n)这四种隔离�U�别�Q�分别有可能产生问题如下所�C�：(x��)</p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; text-align: center; background-color: #ffffff;"><img alt="" width="700" src="http://dl.iteye.com/upload/picture/pic/72610/af5b9c1e-4517-3df2-ad62-af25d1672d12.jpg" height="223" title="点击查看原始大小囄���" style="border: 0px; cursor: url(&quot;/images/magplus.gif&quot;), pointer; vertical-align: middle;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;"><br /></span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">下面�Q�将利用MySQL的客��L(f��ng)���E�序�Q�分别测试几�U�隔��ȝ�别。测试数据库为test�Q�表为tx�Q�表�l�构�Q?/span></p><table border="0" width="440" style="color: #000000; font-family: Helvetica, Tahoma, Arial, sans-serif; font-size: 14px; line-height: 25.2px; height: 50px; background-color: #ffffff;"><tbody><tr><td style="font-size: 1em;"><span style="font-size: medium;">id</span></td><td style="font-size: 1em;"><span style="font-size: medium;">&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;&nbsp;&nbsp; int</span></td></tr><tr><td style="font-size: 1em;"><p style="margin: 0px; padding: 0px;"><span style="font-size: medium;">num</span></p></td><td style="font-size: 1em;"><span style="font-size: medium;">&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;&nbsp;&nbsp; int</span></td></tr></tbody></table><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">两个命��o(h��)行客��L(f��ng)��分别为A�Q�B�Q�不断改变A的隔��ȝ�别，在B端修�Ҏ(gu��)��据�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;"><strong>�Q�一�Q�、将A的隔��ȝ�别设�|��ؓ(f��)read uncommitted(未提交读)</strong></span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;在B未更新数据之前：(x��)</span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端A�Q?/span></strong><img alt="" width="645" src="http://dl.iteye.com/upload/picture/pic/72618/1ca8ec0d-3b6c-3ae1-babc-5dd541c4d1a4.jpg" height="379" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">B更新数据�Q?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端B�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="640" src="http://dl.iteye.com/upload/picture/pic/72620/b37214c3-7726-3306-95ee-1b2fae5ccd6c.jpg" height="397" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端A�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="640" src="http://dl.iteye.com/upload/picture/pic/72622/200d9c94-197a-3fe5-8925-3411cd88555e.jpg" height="481" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">&nbsp;&nbsp;&nbsp;&nbsp;<span style="font-size: medium;">&nbsp;&nbsp;&nbsp; �l�过上面的实验可以得出结论，事务B更新�?ji��n)一条记录，但是没有提交�Q�此时事务A可以查询出未提交记录。造成脏读现象。未提交��L��最低的隔离�U�别�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">�Q�二�Q�、将客户端A的事务隔��ȝ�别设�|��ؓ(f��)read committed(已提交读)</span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;在B未更新数据之前：(x��)</span></p><strong style="font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">客户端A�Q?/span></strong><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><a  style="color: #006600;"><img alt="" width="644" src="http://dl.iteye.com/upload/picture/pic/72626/ae414e52-c216-3bbb-b005-0d972f593456.jpg" height="351" style="border: 0px;" /></a></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">B更新数据�Q?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端B�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="641" src="http://dl.iteye.com/upload/picture/pic/72628/12051f3d-c01e-34b3-a6b6-8b71e1b1dcc8.jpg" height="313" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端A�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="642" src="http://dl.iteye.com/upload/picture/pic/72630/cc80744e-eb9f-3104-bb24-2218e9986d78.jpg" height="351" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �l�过上面的实验可以得出结论，已提交读隔离�U�别解决�?ji��n)脏�ȝ��问题�Q�但是出��C��(ji��n)不可重复�ȝ��问题�Q�即事务A在两�ơ查询的数据不一��_(d��)��因�ؓ(f��)在两�ơ查询之间事务B更新�?ji��n)一条数据。已提交��d��允许��d��已提交的记录�Q�但不要求可重复诅R�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">(�?�?span style="font-size: medium;"><strong>���A的隔��ȝ�别设�|��ؓ(f��)repeatable read(可重复读)</strong></span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;在B未更新数据之前：(x��)</span></p><div style="font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端A�Q?/span></strong></div><div style="font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="643" src="http://dl.iteye.com/upload/picture/pic/72632/0bf52be3-e873-3f3f-8d56-d703a8f678ab.jpg" height="319" style="border: 0px;" /></div><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">B更新数据�Q?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端B�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="645" src="http://dl.iteye.com/upload/picture/pic/72634/e58d1814-bdca-3313-bcf5-339e3678536a.jpg" height="333" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端A�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="640" src="http://dl.iteye.com/upload/picture/pic/72636/83bfe583-2d57-345a-917e-4ee163235b62.jpg" height="497" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">B插入数据�Q?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端B�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="641" src="http://dl.iteye.com/upload/picture/pic/72638/192348aa-4fa5-3d5f-a4f9-4660ddd725cd.jpg" height="366" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">客户端A�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="641" src="http://dl.iteye.com/upload/picture/pic/72640/4398c5b1-434c-3380-ba19-060154cf2070.jpg" height="351" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; �׃��上的实验可以得出�l�论�Q�可重复读隔��ȝ�别只允许��d��已提交记录，而且在一个事务两�ơ读取一个记录期��_(d��)��其他事务部的更新该记录。但该事务不要求与其他事务可串行化。例如，当一个事务可以找到由一个已提交事务更新的记录，但是可能产生�q�读问题(注意是可能，因�ؓ(f��)数据库对隔离�U�别的实现有所差别)。像以上的实验，���没有出现数据���ȝ��问题�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;">(<strong>�?�?span style="font-size: medium;"><strong>���A的隔��ȝ�别设�|��ؓ(f��)&nbsp;</strong></span><span style="font-size: medium;">可串行化&nbsp;(Serializable)</span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">A端打开事务�Q�B端插入一条记�?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">事务A端：(x��)</span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="639" src="http://dl.iteye.com/upload/picture/pic/72642/c604c5ce-311d-3923-8dcd-36b0188f4f31.jpg" height="234" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">事务B端：(x��)</span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="640" src="http://dl.iteye.com/upload/picture/pic/72644/c488f9d9-7da2-3e6d-9a82-2b92d1051afd.jpg" height="141" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">因�ؓ(f��)此时事务A的隔��ȝ�别设�|��ؓ(f��)serializable�Q�开始事务后�Q��ƈ没有提交�Q�所以事务B只能�{�待�?/span></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">事务A提交事务�Q?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">事务A�?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="639" src="http://dl.iteye.com/upload/picture/pic/72646/322ed59a-b2b9-338c-a2f0-09c9b7707577.jpg" height="73" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><strong><span style="font-size: medium;">事务B�?/span></strong></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><img alt="" width="644" src="http://dl.iteye.com/upload/picture/pic/72648/8e60e19b-09af-31a7-b8d3-8e638bbf177c.jpg" height="47" style="border: 0px;" /></p><p style="margin: 0px; padding: 0px; font-family: Helvetica, Tahoma, Arial, sans-serif; line-height: 25.2px; background-color: #ffffff;"><span style="font-size: medium;">&nbsp; &nbsp; &nbsp;&nbsp;<br /></span><span style="line-height: 25.2px;">&nbsp;</span><span style="line-height: 25.2px; font-size: medium;">serializable完全锁定字段�Q�若一个事务来查询同一份数据就必须�{�待�Q�直到前一个事务完成�ƈ解除锁定为止</span><span style="line-height: 25.2px;">&nbsp;�?/span><span style="line-height: 25.2px; font-size: medium;">是完整的隔离�U�别�Q�会(x��)锁定对应的数据表��|��因而会(x��)有效率的问题�?br /><br /></span></p><div>&nbsp;转自�Q�http://xm-king.iteye.com/blog/770721</div><img src ="http://www.aygfsteel.com/qbna350816/aggbug/431834.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.aygfsteel.com/qbna350816/" target="_blank">胡小�?/a> 2016-09-24 00:06 <a href="http://www.aygfsteel.com/qbna350816/archive/2016/09/24/431834.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item></channel></rss>                                                 <footer>
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