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MuiInputBase-sizeSmall MuiInputBase-adornedStart css-10r6rap"><div class="MuiInputAdornment-root MuiInputAdornment-positionStart MuiInputAdornment-outlined MuiInputAdornment-sizeSmall css-1a6giau"><span class="notranslate"></span><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeSmall css-1k33q06" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="SearchIcon"><path d="M15.5 14h-.79l-.28-.27C15.41 12.59 16 11.11 16 9.5 16 5.91 13.09 3 9.5 3S3 5.91 3 9.5 5.91 16 9.5 16c1.61 0 3.09-.59 4.23-1.57l.27.28v.79l5 4.99L20.49 19l-4.99-5zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z"/></svg></div><input type="search" aria-invalid="false" id="doc-search" placeholder="搜索文档" value="" class="MuiInputBase-input MuiOutlinedInput-input MuiInputBase-inputTypeSearch MuiInputBase-inputSizeSmall MuiInputBase-inputAdornedStart css-1a7iucg"/><fieldset aria-hidden="true" class="MuiOutlinedInput-notchedOutline css-igs3ac"><legend class="css-hdw1oc"><span class="notranslate"></span></legend></fieldset></div></div></form></div></div></div></div></header><div class="PingCAP-Doc MuiBox-root css-s1brf2"><div class="MuiBox-root css-hboir5"><aside class="MuiBox-root css-2tzg8"><div class="MuiBox-root css-ysaqso"><button class="MuiButtonBase-root MuiButton-root MuiButton-text MuiButton-textPrimary MuiButton-sizeMedium MuiButton-textSizeMedium MuiButton-disableElevation css-1q0sqyi" tabindex="0" type="button" id="version-select-button" aria-haspopup="true"><div class="MuiTypography-root MuiTypography-body1 css-hg1lfe">v8.1</div><span class="MuiButton-endIcon MuiButton-iconSizeMedium css-pt151d"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium css-1rrdqpg" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></span></button><ul role="tree" id="left-nav-treeview" aria-multiselectable="false" class="MuiTreeView-root css-12mehxg" tabindex="0" aria-label="left navigation"><a class="MuiTypography-root MuiTypography-body1 css-z7v9yr" target="_blank" href="https://docs.pingcap.com/zh" style="text-decoration:none;width:100%;color:inherit"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-0" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><div class="MuiBox-root css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">文档中心</div></div></div></div></div></li></a><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-1" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">关于 TiDB</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-2" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">快速上手</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-3" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">应用开发</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-4" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">部署标准集群</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-5" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">数据迁移</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-6" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">数据集成</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-7" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">运维操作</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-8" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">监控与告警</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-9" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">故障诊断</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-10" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">性能调优</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-11" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">教程</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-12" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">TiDB 工具</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="true" id="left-nav-treeview-0-13" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content Mui-expanded" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-13dmm4z" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">参考指南</div></div></div></div></div><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div class="MuiCollapse-wrapper MuiCollapse-vertical css-hboir5"><div class="MuiCollapse-wrapperInner MuiCollapse-vertical css-8atqhb"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-0" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">架构</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-1" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">存储引擎 TiKV</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-2" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">存储引擎 TiFlash</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-3" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">TiDB 分布式执行框架</div></div></div></div></div></li><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/system-variables"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-4" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><div class="MuiBox-root css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">系统变量</div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/status-variables"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-5" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><div class="MuiBox-root css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">服务器状态变量</div></div></div></div></div></li></a><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-6" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">配置文件参数</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-7" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">CLI</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-8" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">命令行参数</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-9" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">监控指标</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-10" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">权限</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="true" id="left-nav-treeview-0-13-11" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content Mui-expanded" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-13dmm4z" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">SQL</div></div></div></div></div><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div class="MuiCollapse-wrapper MuiCollapse-vertical css-hboir5"><div class="MuiCollapse-wrapperInner MuiCollapse-vertical css-8atqhb"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-11-0" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">SQL 语言结构和语法</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-11-1" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">SQL 语句</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-11-2" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">数据类型</div></div></div></div></div></li><li class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="true" id="left-nav-treeview-0-13-11-3" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content Mui-expanded" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-13dmm4z" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">函数与操作符</div></div></div></div></div><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div class="MuiCollapse-wrapper MuiCollapse-vertical css-hboir5"><div class="MuiCollapse-wrapperInner MuiCollapse-vertical css-8atqhb"><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/functions-and-operators-overview"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-11-3-0" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-3o0h5k"/><div 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css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">Cast 函数和操作符</div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/encryption-and-compression-functions"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-11-3-9" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">加密和压缩函数</div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/locking-functions"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-11-3-10" tabindex="-1" 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class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-11-3-12" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">JSON 函数</div></div></div></div></div></li><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/aggregate-group-by-functions"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-11-3-13" tabindex="-1" 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修饰符</div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/window-functions"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-11-3-15" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">窗口函数</div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/miscellaneous-functions"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-13-11-3-16" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div 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class="MuiTreeItem-root css-14t19hb" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-15" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-hkir54" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">版本发布历史</div></div></div></div></div></li><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/glossary"><li class="MuiTreeItem-root css-14t19hb" role="treeitem" id="left-nav-treeview-0-16" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-zfdk9c MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><div class="MuiBox-root css-3o0h5k"/><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1rc6ywa">术语表</div></div></div></div></div></li></a></ul></div></aside><main class="MuiBox-root css-sb2sd0"><div class="MuiBox-root css-w0vdto"><div class="css-1q5cbag"><div class="MuiBox-root css-was4pq"><div class="MuiContainer-root MuiContainer-maxWidthLg MuiContainer-disableGutters doc-content css-5csqms"><div class="markdown-body MuiBox-root css-0"><h1 id="cast-函数和操作符" style="position:relative">Cast 函数和操作符<a href="#cast-%E5%87%BD%E6%95%B0%E5%92%8C%E6%93%8D%E4%BD%9C%E7%AC%A6" aria-label="cast 函数和操作符 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h1><p>Cast 函数和操作符用于将某种数据类型的值转换为另一种数据类型。TiDB 支持使用 MySQL 8.0 中提供的所有 <a href="https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html" target="_blank" referrerpolicy="no-referrer-when-downgrade">Cast 函数和操作符</a>。</p><h2 id="cast-函数和操作符表" style="position:relative">Cast 函数和操作符表<a href="#cast-%E5%87%BD%E6%95%B0%E5%92%8C%E6%93%8D%E4%BD%9C%E7%AC%A6%E8%A1%A8" aria-label="cast 函数和操作符表 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><table><thead><tr><th>函数和操作符名</th><th>功能描述</th></tr></thead><tbody><tr><td><a href="#binary"><code>BINARY</code></a></td><td>将一个字符串转换成一个二进制字符串</td></tr><tr><td><a href="#cast"><code>CAST()</code></a></td><td>将一个值转换成一个确定类型</td></tr><tr><td><a href="#convert"><code>CONVERT()</code></a></td><td>将一个值转换成一个确定类型</td></tr></tbody></table><div class="MuiBox-root css-1weqspv"><div class="MuiPaper-root MuiPaper-elevation MuiPaper-rounded MuiPaper-elevation0 MuiAlert-root MuiAlert-standardInfo MuiAlert-standard css-1bzshic" role="alert"><div class="MuiAlert-icon css-1l54tgj"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="InfoOutlinedIcon"><path d="M11,9H13V7H11M12,20C7.59,20 4,16.41 4,12C4,7.59 7.59,4 12,4C16.41,4 20,7.59 20, 12C20,16.41 16.41,20 12,20M12,2A10,10 0 0,0 2,12A10,10 0 0,0 12,22A10,10 0 0,0 22,12A10, 10 0 0,0 12,2M11,17H13V11H11V17Z"/></svg></div><div class="MuiAlert-message css-1xsto0d"><div class="MuiTypography-root MuiTypography-body1 MuiTypography-gutterBottom MuiAlertTitle-root css-o4nulc">注意</div><p>TiDB 和 MySQL 对于 <code>SELECT CAST(MeN AS CHAR)</code>（或者等价的 <code>SELECT CONVERT(MeM, CHAR)</code>）的结果显示不一致，其中 <code>MeN</code> 是用科学计数法表示的双精度浮点数。MySQL 在 <code>-15 &lt;= N &lt;= 14</code> 时显示完整数值，在 <code>N &lt; -15</code> 或 <code>N &gt; 14</code> 时显示科学计数法。而 TiDB 始终显示完整数值。例如，MySQL 对于 <code>SELECT CAST(3.1415e15 AS CHAR)</code> 的显示结果为 <code>3.1415e15</code>，而 TiDB 的显示结果为 <code>3141500000000000</code>。</p></div></div></div><h2 id="binary" style="position:relative">BINARY<a href="#binary" aria-label="binary permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><p><a href="https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#operator_binary" target="_blank" referrerpolicy="no-referrer-when-downgrade"><code>BINARY</code></a> 运算符从 MySQL 8.0.27 版本起已被废弃。建议在 TiDB 和 MySQL 中都改用 <code>CAST(... AS BINARY)</code>。</p><h2 id="cast" style="position:relative">CAST<a href="#cast" aria-label="cast permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><p><a href="https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_cast" target="_blank" referrerpolicy="no-referrer-when-downgrade"><code>CAST(&lt;expression&gt; AS &lt;type&gt; [ARRAY])</code></a> 函数用于将一个表达式的值转换为指定的数据类型。</p><p>此外，你还可以将该函数用于创建<a href="/zh/tidb/stable/sql-statement-create-index#多值索引">多值索引</a>。</p><p>支持的数据类型包括：</p><table><thead><tr><th>类型</th><th>描述</th><th>是否可用于多值索引</th></tr></thead><tbody><tr><td><code>BINARY(n)</code></td><td>二进制字符串</td><td>否</td></tr><tr><td><code>CHAR(n)</code></td><td>字符串</td><td>是，但仅当指定了长度时才有效</td></tr><tr><td><code>DATE</code></td><td>日期</td><td>是</td></tr><tr><td><code>DATETIME(fsp)</code></td><td>日期/时间，其中 <code>fsp</code> 是可选的</td><td>是</td></tr><tr><td><code>DECIMAL(n, m)</code></td><td>十进制数，其中 <code>n</code> 和 <code>m</code> 是可选的，如果未指定，则默认为 <code>10</code> 和 <code>0</code></td><td>否</td></tr><tr><td><code>DOUBLE</code></td><td>双精度浮点数</td><td>否</td></tr><tr><td><code>FLOAT(n)</code></td><td>浮点数，其中 <code>n</code> 是可选的，应介于 <code>0</code> 和 <code>53</code> 之间</td><td>否</td></tr><tr><td><code>JSON</code></td><td>JSON</td><td>否</td></tr><tr><td><code>REAL</code></td><td>浮点数</td><td>是</td></tr><tr><td><code>SIGNED [INTEGER]</code></td><td>有符号整数</td><td>是</td></tr><tr><td><code>TIME(fsp)</code></td><td>时间</td><td>是</td></tr><tr><td><code>UNSIGNED [INTEGER]</code></td><td>无符号整数</td><td>是</td></tr><tr><td><code>YEAR</code></td><td>年</td><td>否</td></tr></tbody></table><p>示例：</p><p>以下语句将二进制字符串从十六进制文字转换为 <code>CHAR</code>。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">SELECT</span> <span class="hljs-built_in">CAST</span>(<span class="hljs-number">0x54694442</span> <span class="hljs-keyword">AS</span> <span class="hljs-type">CHAR</span>); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">--------------------------+</span> <span class="hljs-operator">|</span> <span class="hljs-built_in">CAST</span>(<span class="hljs-number">0x54694442</span> <span class="hljs-keyword">AS</span> <span class="hljs-type">CHAR</span>) <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">--------------------------+</span> <span class="hljs-operator">|</span> TiDB <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">--------------------------+</span> <span class="hljs-number">1</span> <span class="hljs-type">row</span> <span class="hljs-keyword">in</span> <span class="hljs-keyword">set</span> (<span class="hljs-number">0.0002</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><p>以下语句将从 JSON 列中提取的 <code>a</code> 属性的值转换为无符号数组。需要注意的是，该函数只有作为多值索引定义的一部分时，才支持将数据转换为数组。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t ( id <span class="hljs-type">INT</span> <span class="hljs-keyword">PRIMARY</span> KEY, j JSON, INDEX idx_a ((<span class="hljs-built_in">CAST</span>(j<span class="hljs-operator">-</span><span class="hljs-operator">&gt;</span><span class="hljs-string">'$.a'</span> <span class="hljs-keyword">AS</span> UNSIGNED <span class="hljs-keyword">ARRAY</span>))) <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t <span class="hljs-keyword">VALUES</span> (<span class="hljs-number">1</span>, <span class="hljs-built_in">JSON_OBJECT</span>(<span class="hljs-string">'a'</span>,<span class="hljs-built_in">JSON_ARRAY</span>(<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>))); <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t <span class="hljs-keyword">VALUES</span> (<span class="hljs-number">2</span>, <span class="hljs-built_in">JSON_OBJECT</span>(<span class="hljs-string">'a'</span>,<span class="hljs-built_in">JSON_ARRAY</span>(<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,<span class="hljs-number">6</span>))); <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t <span class="hljs-keyword">VALUES</span> (<span class="hljs-number">3</span>, <span class="hljs-built_in">JSON_OBJECT</span>(<span class="hljs-string">'a'</span>,<span class="hljs-built_in">JSON_ARRAY</span>(<span class="hljs-number">7</span>,<span class="hljs-number">8</span>,<span class="hljs-number">9</span>))); ANALYZE <span class="hljs-keyword">TABLE</span> t; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"> EXPLAIN <span class="hljs-keyword">SELECT</span> <span class="hljs-operator">*</span> <span class="hljs-keyword">FROM</span> t <span class="hljs-keyword">WHERE</span> <span class="hljs-number">1</span> <span class="hljs-keyword">MEMBER</span> <span class="hljs-keyword">OF</span>(j<span class="hljs-operator">-</span><span class="hljs-operator">&gt;</span><span class="hljs-string">'$.a'</span>)\G <span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span> <span class="hljs-number">1.</span> <span class="hljs-type">row</span> <span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span> id: IndexMerge_10 estRows: <span class="hljs-number">2.00</span> task: root access object: operator info: type: <span class="hljs-keyword">union</span> <span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span> <span class="hljs-number">2.</span> <span class="hljs-type">row</span> <span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span> id: ├─IndexRangeScan_8(Build) estRows: <span class="hljs-number">2.00</span> task: cop[tikv] access object: <span class="hljs-keyword">table</span>:t, index:idx_a(<span class="hljs-built_in">cast</span>(json_extract(`j`, _utf8mb4<span class="hljs-string">'$.a'</span>) <span class="hljs-keyword">as</span> unsigned <span class="hljs-keyword">array</span>)) operator info: <span class="hljs-keyword">range</span>:[<span class="hljs-number">1</span>,<span class="hljs-number">1</span>], keep <span class="hljs-keyword">order</span>:<span class="hljs-literal">false</span>, stats:partial[j:unInitialized] <span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span> <span class="hljs-number">3.</span> <span class="hljs-type">row</span> <span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span><span class="hljs-operator">*</span> id: └─TableRowIDScan_9(Probe) estRows: <span class="hljs-number">2.00</span> task: cop[tikv] access object: <span class="hljs-keyword">table</span>:t operator info: keep <span class="hljs-keyword">order</span>:<span class="hljs-literal">false</span>, stats:partial[j:unInitialized] <span class="hljs-number">3</span> <span class="hljs-keyword">rows</span> <span class="hljs-keyword">in</span> <span class="hljs-keyword">set</span> (<span class="hljs-number">0.00</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><h2 id="convert" style="position:relative">CONVERT<a href="#convert" aria-label="convert permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><p><a href="https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_convert" target="_blank" referrerpolicy="no-referrer-when-downgrade"><code>CONVERT()</code></a> 函数用于在<a href="/zh/tidb/stable/character-set-and-collation">字符集</a>之间进行转换。</p><p>示例：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">CONVERT</span>(<span class="hljs-number">0x616263</span> <span class="hljs-keyword">USING</span> utf8mb4); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">---------------------------------+</span>