https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/Recent content in 基础 on Elastic CodeHugo -- gohugo.iozh-cn© 2026 Elastic Codehttps://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%B8%89%E8%8C%83%E5%BC%8F/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%B8%89%E8%8C%83%E5%BC%8F/<h2 class="relative group">第一范式 <div id="第一范式" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%ac%ac%e4%b8%80%e8%8c%83%e5%bc%8f" aria-label="锚点">#</a> </span> </h2> <h2 class="relative group">第二范式 <div id="第二范式" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%ac%ac%e4%ba%8c%e8%8c%83%e5%bc%8f" aria-label="锚点">#</a> </span> </h2> <h2 class="relative group">第三范式 <div id="第三范式" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%ac%ac%e4%b8%89%e8%8c%83%e5%bc%8f" aria-label="锚点">#</a> </span> </h2> <h2 class="relative group">反范式 <div id="反范式" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%8f%8d%e8%8c%83%e5%bc%8f" aria-label="锚点">#</a> </span> </h2>https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%BA%8B%E5%8A%A1/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%BA%8B%E5%8A%A1/<h2 class="relative group">概念 <div id="概念" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%a6%82%e5%bf%b5" aria-label="锚点">#</a> </span> </h2> <p><figure><img class="my-0 rounded-md" loading="lazy" decoding="async" fetchpriority="auto" alt="" width="1876" height="566" src="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%BA%8B%E5%8A%A1/static/OzJGbZjDBo0nJHxqSaWcEGlTnjc_hu_fc109e55a9307d69.png" srcset="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%BA%8B%E5%8A%A1/static/OzJGbZjDBo0nJHxqSaWcEGlTnjc_hu_fc109e55a9307d69.png 800w, https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%BA%8B%E5%8A%A1/static/OzJGbZjDBo0nJHxqSaWcEGlTnjc_hu_26f3535b647b7f0d.png 1280w" sizes="(min-width: 768px) 50vw, 65vw" data-zoom-src="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E4%BA%8B%E5%8A%A1/static/OzJGbZjDBo0nJHxqSaWcEGlTnjc.png"></figure> </p> <h2 class="relative group">ACID 特性 <div id="acid-特性" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#acid-%e7%89%b9%e6%80%a7" aria-label="锚点">#</a> </span> </h2> <p>原子性 **Atomicity **：要么全部执行，要么全部不执行</p>https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%88%86%E7%BB%84%E8%81%9A%E5%90%88/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%88%86%E7%BB%84%E8%81%9A%E5%90%88/https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%A2%9E%E5%88%A0%E6%94%B9%E6%9F%A5/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%A2%9E%E5%88%A0%E6%94%B9%E6%9F%A5/https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%AD%90%E6%9F%A5%E8%AF%A2/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%AD%90%E6%9F%A5%E8%AF%A2/https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%AD%98%E5%82%A8%E5%BC%95%E6%93%8E/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E5%AD%98%E5%82%A8%E5%BC%95%E6%93%8E/<h2 class="relative group">InnoDB <div id="innodb" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#innodb" aria-label="锚点">#</a> </span> </h2> <h2 class="relative group">Myisam <div id="myisam" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#myisam" aria-label="锚点">#</a> </span> </h2> <div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-sql" data-lang="sql"><span style="display:flex;"><span><span style="color:#f92672">#</span> <span style="color:#66d9ef">show</span> engines; </span></span><span style="display:flex;"><span><span style="color:#66d9ef">alter</span> <span style="color:#66d9ef">table</span> tb_user_pp engine <span style="color:#f92672">=</span> myisam;</span></span></code></pre></div></div> <h2 class="relative group">Memory <div id="memory" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#memory" aria-label="锚点">#</a> </span> </h2>https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E5%BA%93%E7%AE%A1%E7%90%86/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E5%BA%93%E7%AE%A1%E7%90%86/https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B/<h2 class="relative group">数据类型 <div id="数据类型" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%95%b0%e6%8d%ae%e7%b1%bb%e5%9e%8b" aria-label="锚点">#</a> </span> </h2> <h3 class="relative group">整型（TINYINT, SMALLINT, MEDIUMINT, INT, BIGINT） <div id="整型tinyint-smallint-mediumint-int-bigint" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%95%b4%e5%9e%8btinyint-smallint-mediumint-int-bigint" aria-label="锚点">#</a> </span> </h3> <h3 class="relative group">字符串类型（CHAR, VARCHAR） <div id="字符串类型char-varchar" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%ad%97%e7%ac%a6%e4%b8%b2%e7%b1%bb%e5%9e%8bchar-varchar" aria-label="锚点">#</a> </span> </h3> <h3 class="relative group">日期类型（DATE, TIME, DATETIME, TIMESTAMP） <div id="日期类型date-time-datetime-timestamp" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%97%a5%e6%9c%9f%e7%b1%bb%e5%9e%8bdate-time-datetime-timestamp" aria-label="锚点">#</a> </span> </h3> <h3 class="relative group">浮点数（FLOAT, DOUBLE, DECIMAL） <div id="浮点数float-double-decimal" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%b5%ae%e7%82%b9%e6%95%b0float-double-decimal" aria-label="锚点">#</a> </span> </h3> <h3 class="relative group">大对象（TEXT, BLOB） <div id="大对象text-blob" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%a4%a7%e5%af%b9%e8%b1%a1text-blob" aria-label="锚点">#</a> </span> </h3> <h3 class="relative group">NULL 值 <div id="null-值" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#null-%e5%80%bc" aria-label="锚点">#</a> </span> </h3> <h2 class="relative group">数据类型存储方式 <div id="数据类型存储方式" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%95%b0%e6%8d%ae%e7%b1%bb%e5%9e%8b%e5%ad%98%e5%82%a8%e6%96%b9%e5%bc%8f" aria-label="锚点">#</a> </span> </h2> <p><figure><img class="my-0 rounded-md" loading="lazy" decoding="async" fetchpriority="auto" alt="" width="1380" height="1222" src="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B/static/BsdhbxAYyoK1Bgxp0kzcpqbjn2d_hu_f745e11dfc9536a1.png" srcset="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B/static/BsdhbxAYyoK1Bgxp0kzcpqbjn2d_hu_f745e11dfc9536a1.png 800w, https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B/static/BsdhbxAYyoK1Bgxp0kzcpqbjn2d_hu_2db5c730f0f0e25b.png 1280w" sizes="(min-width: 768px) 50vw, 65vw" data-zoom-src="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B/static/BsdhbxAYyoK1Bgxp0kzcpqbjn2d.png"></figure> </p>https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E7%B4%A2%E5%BC%95/Mon, 01 Jan 0001 00:00:00 +0000https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E7%B4%A2%E5%BC%95/<p>如下图为图书馆的图书摆放，仔细体会索引的奥义</p> <p><figure><img class="my-0 rounded-md" loading="lazy" decoding="async" fetchpriority="auto" alt="" width="904" height="658" src="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E7%B4%A2%E5%BC%95/static/K4dCb8msnoyhYexbAu7cdhW2nie_hu_d26eed587ff3f29c.png" srcset="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E7%B4%A2%E5%BC%95/static/K4dCb8msnoyhYexbAu7cdhW2nie_hu_d26eed587ff3f29c.png 800w, https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E7%B4%A2%E5%BC%95/static/K4dCb8msnoyhYexbAu7cdhW2nie.png 1280w" sizes="(min-width: 768px) 50vw, 65vw" data-zoom-src="https://my.elastic-code.com/zh/docs/mysql/%E5%9F%BA%E7%A1%80/%E7%B4%A2%E5%BC%95/static/K4dCb8msnoyhYexbAu7cdhW2nie.png"></figure> </p> <p>目的：加快较慢的查询</p> <p>注意：基于查询创建索引，而不是基于表创建索引！</p> <h4 class="relative group">创建、查看索引 <div id="创建查看索引" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%88%9b%e5%bb%ba%e6%9f%a5%e7%9c%8b%e7%b4%a2%e5%bc%95" aria-label="锚点">#</a> </span> </h4> <p>自定义索引通常称为二级索引，创建二级索引后，MySQL 会自动将主键 id 存储到该索引中。该索引中的每个记录都包含索引对应字段的值 和主键 id</p>