<?xml version="1.0" encoding="utf-8" ?><rss version="2.0"><channel><title><![CDATA[qq_32076957的博客]]></title><description><![CDATA[]]></description><link>https://blog.youkuaiyun.com/qq_32076957</link><language>zh-cn</language><generator>https://blog.youkuaiyun.com/</generator><copyright><![CDATA[Copyright &copy; qq_32076957]]></copyright><item><title><![CDATA[SQL优化（四）执行计划之表连接]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/142456303</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/142456303</guid><author>qq_32076957</author><pubDate>Sat, 12 Oct 2024 01:20:36 +0800</pubDate><description><![CDATA[表连接方式]]></description><category></category></item><item><title><![CDATA[SQL优化（三）执行计划之访问路径]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/140810326</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/140810326</guid><author>qq_32076957</author><pubDate>Mon, 23 Sep 2024 13:44:56 +0800</pubDate><description><![CDATA[例如，假设一个索引块存储100行数据，现在要访问10000条数据，需要扫描100个索引叶子块，如果此时需要回表，这些数据可能分布在上千个块上，如果没有缓存，则需要进行上千次IO，性能影响相当严重。当需要从表中查询出大量数据但是只需要获取表中部分列的数据的，例如只取出2~5个列，正常情况返回大量数据应该走全表扫描，由于Oracle是行存储数据库，读一行就要扫描所有列，这种情况下可以创建组合索引走索引快速全扫描，避免扫描过多的列。对于分区表，如果是多分区，那么同时扫描多个分区，如果是单分区，则同时扫描多个区。]]></description><category></category></item><item><title><![CDATA[POI生成Excel文件增加数据验证（下拉序列）]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/142183035</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/142183035</guid><author>qq_32076957</author><pubDate>Fri, 13 Sep 2024 11:28:26 +0800</pubDate><description><![CDATA[由于excel数据验证 序列的长度最多255字符， 如果代码中数据的长度超过这个，则生成的excel会提示先修复才能打开，修复完成打开之后发现需要设置数据验证的列没有设置成功。如果想要输入更多数据，则先可以先把数据保存到一个隐藏的sheet中，然后通过公式引用存储的数据再设置数据验证。POI版本为5.2.2。]]></description><category></category></item><item><title><![CDATA[SQL优化（二）统计信息]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/142069781</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/142069781</guid><author>qq_32076957</author><pubDate>Tue, 10 Sep 2024 21:13:22 +0800</pubDate><description><![CDATA[数据库的统计信息非常重要，如果没有正确地收集表的统计信息，或者没有及时地更新表的统计信息，SQL就有可能走错执行计划，也就会出现性能问题。统计信息主要分为系统的统计信息、数据字典的统计信息以及动态性能视图基表的统计信息，我们主要关注表、列、索引的统计信息。注：本文涉及到的数据库版本为Oracle Database 19c Enterprise Edition Release表的统计信息主要包含表的以及​，通过查询数据字典获取表的统计信息。]]></description><category></category></item><item><title><![CDATA[SQL优化（一）基础概念]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/140737947</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/140737947</guid><author>qq_32076957</author><pubDate>Tue, 30 Jul 2024 00:39:08 +0800</pubDate><description><![CDATA[SQL优化涉及到的概念]]></description><category></category></item><item><title><![CDATA[windows系统下安装fnm]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/139567420</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/139567420</guid><author>qq_32076957</author><pubDate>Mon, 10 Jun 2024 01:19:42 +0800</pubDate><description><![CDATA[由于最近做项目要切换多个node版本，查询了一下常用的有nvm和fnm这两种，对比了一下选择了fnm。]]></description><category></category></item><item><title><![CDATA[JDK常用性能监控和故障处理工具]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/132724301</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/132724301</guid><author>qq_32076957</author><pubDate>Tue, 31 Oct 2023 22:33:36 +0800</pubDate><description><![CDATA[jdk命令行、jcmd、jinfo、jstack、jmap]]></description><category></category></item><item><title><![CDATA[docker快速安装开发用各种数据库]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/133761875</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/133761875</guid><author>qq_32076957</author><pubDate>Wed, 11 Oct 2023 13:18:04 +0800</pubDate><description><![CDATA[docker、数据库、oracle、Mysql、mssql、highgo、kingbase、postgres、dm8]]></description><category></category></item><item><title><![CDATA[常用的字符集和字符编码]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/132584177</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/132584177</guid><author>qq_32076957</author><pubDate>Tue, 05 Sep 2023 15:05:41 +0800</pubDate><description><![CDATA[编码格式、UTF-8、ASCII、GB2312]]></description><category></category></item><item><title><![CDATA[Base64]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/129553848</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/129553848</guid><author>qq_32076957</author><pubDate>Sat, 15 Apr 2023 23:24:31 +0800</pubDate><description><![CDATA[base64]]></description><category></category></item><item><title><![CDATA[用Wireshark分析TLS（v1.2）]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/129430270</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/129430270</guid><author>qq_32076957</author><pubDate>Sun, 19 Mar 2023 13:15:14 +0800</pubDate><description><![CDATA[Wireshark，TLS]]></description><category></category></item><item><title><![CDATA[X.509证书]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/129416516</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/129416516</guid><author>qq_32076957</author><pubDate>Thu, 09 Mar 2023 18:00:02 +0800</pubDate><description><![CDATA[X.509证书]]></description><category></category></item><item><title><![CDATA[HTTPS]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/129298628</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/129298628</guid><author>qq_32076957</author><pubDate>Thu, 09 Mar 2023 01:13:53 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+0800</pubDate><description><![CDATA[nginx.conf]]></description><category></category></item><item><title><![CDATA[OpenSSL]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/128761546</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/128761546</guid><author>qq_32076957</author><pubDate>Thu, 09 Feb 2023 00:42:11 +0800</pubDate><description><![CDATA[openssl]]></description><category></category></item><item><title><![CDATA[（十一）椭圆曲线密码（ECC）]]></title><link>https://blog.youkuaiyun.com/qq_32076957/article/details/128935830</link><guid>https://blog.youkuaiyun.com/qq_32076957/article/details/128935830</guid><author>qq_32076957</author><pubDate>Wed, 08 Feb 2023 18:13:32 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