【MySQL语句】MySQL基础语句，应付期末考试，木得问题~

作者: HUI 发布: 2022年5月10日 20阅读 0评论

🦞数据库的操作

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<span class="token keyword">show</span> <span class="token keyword">databases</span><span class="token punctuation">;</span>

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🦞数据库的操作

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<span class="token keyword">show</span> <span class="token keyword">databases</span><span class="token punctuation">;</span>

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<span class="token keyword">create</span> <span class="token keyword">database</span> <span class="token punctuation">[</span><span class="token keyword">if</span> <span class="token operator">not</span> <span class="token keyword">exists</span><span class="token punctuation">]</span> 数据库名<span class="token punctuation">;</span>

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<span class="token keyword">use</span> 数据库名<span class="token punctuation">;</span>

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<span class="token keyword">drop</span> <span class="token keyword">database</span> <span class="token punctuation">[</span><span class="token keyword">if</span> <span class="token keyword">exists</span><span class="token punctuation">]</span> 数据库名<span class="token punctuation">;</span>

🦞表的操作

（使用表的操作时，要先使用数据库）

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<span class="token keyword">create</span> <span class="token keyword">table</span> 表名 <span class="token punctuation">(</span> 字段名称 字段类型<span class="token punctuation">,</span> 字段名称 字段类型<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>

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<span class="token keyword">desc</span> 表名<span class="token punctuation">;</span>

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<span class="token keyword">show</span> <span class="token keyword">tables</span><span class="token punctuation">;</span>

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<span class="token keyword">drop</span> <span class="token keyword">table</span> <span class="token punctuation">[</span><span class="token keyword">if</span> <span class="token keyword">exists</span><span class="token punctuation">]</span> 表名<span class="token punctuation">;</span>

🦞插入操作

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<span class="token keyword">insert</span> <span class="token keyword">into</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">values</span> <span class="token punctuation">(</span>对应的列的数据<span class="token punctuation">)</span><span class="token punctuation">;</span>

数据的顺序和列名的顺序要一致。

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<span class="token keyword">insert</span> <span class="token keyword">into</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token punctuation">(</span>若干个指定列<span class="token punctuation">)</span> <span class="token keyword">values</span> <span class="token punctuation">(</span>对应的列的数据<span class="token punctuation">)</span><span class="token punctuation">;</span>

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<span class="token keyword">insert</span> <span class="token keyword">into</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">values</span> <span class="token punctuation">(</span>对应的列的数据<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token punctuation">(</span>对应的列的数据<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>

🦞查询操作

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<span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span><span class="token punctuation">;</span>

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<span class="token keyword">select</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span><span class="token punctuation">;</span>

as可以省略

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<span class="token keyword">select</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token punctuation">(</span><span class="token keyword">as</span><span class="token punctuation">)</span> <span class="token punctuation">[</span>别名<span class="token punctuation">]</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span><span class="token punctuation">;</span>

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<span class="token keyword">select</span> distinc <span class="token punctuation">[</span>若干个列名<span class="token punctuation">]</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span><span class="token punctuation">;</span>

用到WHERE子句

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<span class="token keyword">select</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">where</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>

其中：

  • 比较运算符
  • 逻辑运算符

查询结果根据某一列数据进行排序。

  • ASC：升序
  • DESC：降序
  • NULL 数据，视为比任何值都小，升序在最上面，降序则在最下面

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<span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">order</span> <span class="token keyword">by</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token punctuation">(</span><span class="token keyword">asc</span> 或 <span class="token keyword">desc</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

根据where条件限制后，再根据order by 排序，最后得到排序结果在A和B之间的查询结果。

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<span class="token keyword">select</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">where</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">order</span> <span class="token keyword">by</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">limit</span> A <span class="token keyword">offset</span> B<span class="token punctuation">;</span>

根据某一列进行分组

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<span class="token keyword">select</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span><span class="token punctuation">;</span>

🦞修改操作

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<span class="token keyword">update</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">set</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span>修改的值<span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span>列名<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span>修改的值<span class="token punctuation">]</span> <span class="token keyword">where</span> 子句<span class="token punctuation">;</span>

🦞删除操作

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<span class="token keyword">delete</span> <span class="token keyword">from</span> <span class="token punctuation">[</span>表名<span class="token punctuation">]</span> <span class="token keyword">where</span> <span class="token punctuation">[</span>筛选条件<span class="token punctuation">]</span><span class="token punctuation">;</span>

🦀推荐阅读

🌻未来可期

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作者: HUI

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