http://shimamura.vip/tags/mysql/Recent content in MySQL on IT技术交流Hugozh-cnSun, 02 Aug 2026 17:17:21 +0800http://shimamura.vip/posts/mysql_dql/Sun, 02 Aug 2026 17:17:21 +0800http://shimamura.vip/posts/mysql_dql/<h2 id="示例表格">示例表格</h2> <p>s</p> <table> <thead> <tr> <th>sno</th> <th>sname</th> <th>sex</th> <th>age</th> <th>createtime</th> <th>address</th> <th>did</th> </tr> </thead> <tbody> <tr> <td>S01</td> <td>陈宇乐</td> <td>男</td> <td>21</td> <td>2022-02-02 00:00:00</td> <td>浙江义乌</td> <td>1</td> </tr> <tr> <td>S02</td> <td>陈紫樱</td> <td>女</td> <td>20</td> <td>2022-02-10 00:00:00</td> <td></td> <td>1</td> </tr> <tr> <td>S03</td> <td>杜陈宇</td> <td>男</td> <td>21</td> <td>NULL</td> <td>NULL</td> <td>1</td> </tr> <tr> <td>S04</td> <td>陈宇乐</td> <td>男</td> <td>23</td> <td>NULL</td> <td>NULL</td> <td>2</td> </tr> <tr> <td>S05</td> <td>陈樱</td> <td>女</td> <td>21</td> <td>NULL</td> <td>NULL</td> <td>2</td> </tr> <tr> <td>S06</td> <td>杜佳佳</td> <td>男</td> <td>19</td> <td>NULL</td> <td>NULL</td> <td>NULL</td> </tr> </tbody> </table> <p>d</p> <table> <thead> <tr> <th>did</th> <th>dname</th> </tr> </thead> <tbody> <tr> <td>1</td> <td>计算机系</td> </tr> <tr> <td>2</td> <td>土木工程系</td> </tr> <tr> <td>3</td> <td>英语系</td> </tr> </tbody> </table> <h2 id="一-查询基础">一、 查询基础</h2> <h3 id="11-select-操作">1.1 select 操作</h3> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-sql" data-lang="sql"><span style="display:flex;"><span><span style="color:#f92672">#</span><span style="color:#960050;background-color:#1e0010">查询所有学生信息</span> </span></span><span style="display:flex;"><span><span style="color:#66d9ef">SELECT</span> <span style="color:#f92672">*</span> <span style="color:#66d9ef">FROM</span> student </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#f92672">#</span><span style="color:#960050;background-color:#1e0010">查询学生表中的学号与姓名</span> </span></span><span style="display:flex;"><span><span style="color:#66d9ef">SELECT</span> sno,sname <span style="color:#66d9ef">FROM</span> student </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#f92672">#</span><span style="color:#960050;background-color:#1e0010">查询学生表中的学号与姓名，并且给一个字段别名</span> </span></span><span style="display:flex;"><span><span style="color:#66d9ef">SELECT</span> sno <span style="color:#66d9ef">AS</span> studentNO,sname <span style="color:#66d9ef">AS</span> <span style="color:#e6db74">&#39;姓名&#39;</span> <span style="color:#66d9ef">FROM</span> student </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#f92672">#</span><span style="color:#960050;background-color:#1e0010">查询学生表中的姓名信息，并过滤掉相同姓名信息</span> </span></span><span style="display:flex;"><span><span style="color:#66d9ef">SELECT</span> <span style="color:#66d9ef">DISTINCT</span> sname <span style="color:#66d9ef">FROM</span> student </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#f92672">#</span><span style="color:#960050;background-color:#1e0010">查询学生个数，年龄总和，平均年龄，最大年龄，最小年龄，并给他们一个别名</span> </span></span><span style="display:flex;"><span><span style="color:#66d9ef">SELECT</span> <span style="color:#66d9ef">COUNT</span>(<span style="color:#f92672">*</span>) <span style="color:#66d9ef">AS</span> <span style="color:#e6db74">&#39;学生个数&#39;</span> <span style="color:#960050;background-color:#1e0010">，</span><span style="color:#66d9ef">SUM</span>(age) <span style="color:#66d9ef">AS</span> sumage <span style="color:#66d9ef">FROM</span> student </span></span></code></pre></div><h3 id="12-where">1.2 where</h3> <p>参考SQL</p>