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21 lines
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21 lines
3.2 KiB
HTML
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<h1>SQL FIRST() 函数</h1>
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<h2>FIRST() 函数</h2> <p>FIRST() 函数返回指定的列中第一个记录的值。</p> <h3>SQL FIRST() 语法</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT FIRST(column_name) FROM table_name;</div></code></pre></div> <p><b>注释：</b>只有 MS Access 支持 FIRST() 函数。</p> <h2>SQL Server、MySQL 和 Oracle 中的 SQL FIRST() 工作区</h2> <h3>SQL Server 语法</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT TOP 1 <em>column_name</em> FROM <em>table_name<br/></em>ORDER BY<em> column_name </em>ASC;</div></code></pre></div> <h3>实例</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT TOP 1 CustomerName FROM Customers<br/>ORDER BY CustomerID ASC;</div></code></pre></div> <h3>MySQL 语法</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT <em>column_name</em> FROM <em>table_name</em><br/> ORDER BY <em>column_name</em> ASC<br/>LIMIT 1;</div></code></pre></div> <h3>实例</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT CustomerName FROM Customers<br/>ORDER BY CustomerID ASC<br/>LIMIT 1;</div></code></pre></div> <h3>Oracle 语法</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT <em>column_name </em>FROM <em>table_name</em><br/>ORDER BY <em> column_name </em>ASC<br/>WHERE ROWNUM <=1;</div></code></pre></div> <h3>实例</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT CustomerName FROM Customers<br/>ORDER BY CustomerID ASC<br/>WHERE ROWNUM <=1;</div></code></pre></div> <h2>演示数据库</h2> <p>在本教程中，我们将使用众所周知的 Northwind 样本数据库。</p> <p>下面是选自 "Customers" 表的数据：</p> <table class="reference notranslate">
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<tr>
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<th>CustomerID</th> <th>CustomerName</th> <th>ContactName</th> <th>Address</th> <th>City</th> <th>PostalCode</th> <th>Country</th> </tr>
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<td>1<br/><br/>
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</td> <td>Alfreds Futterkiste</td> <td>Maria Anders</td> <td>Obere Str. 57</td> <td>Berlin</td> <td>12209</td> <td>Germany</td> </tr>
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<td>2</td> <td>Ana Trujillo Emparedados y helados</td> <td>Ana Trujillo</td> <td>Avda. de la Constitución 2222</td> <td>México D.F.</td> <td>05021</td> <td>Mexico</td> </tr>
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<td>3</td> <td>Antonio Moreno Taquería</td> <td>Antonio Moreno</td> <td>Mataderos 2312</td> <td>México D.F.</td> <td>05023</td> <td>Mexico</td> </tr>
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<td>4<br/><br/>
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</td> <td>Around the Horn</td> <td>Thomas Hardy</td> <td>120 Hanover Sq.</td> <td>London</td> <td>WA1 1DP</td> <td>UK</td> </tr>
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<td>5</td> <td>Berglunds snabbköp</td> <td>Christina Berglund</td> <td>Berguvsvägen 8</td> <td>Luleå</td> <td>S-958 22</td> <td>Sweden</td> </tr>
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<h2>SQL FIRST() 实例</h2> <p>下面的 SQL 语句选取 "Customers" 表的 "CustomerName" 列中第一个记录的值：</p> <div class="example margin-b-10"> <h2 class="example">实例</h2> <pre><code class="language-sql"><div class="example_code notranslate"> SELECT FIRST(CustomerName) AS FirstCustomer FROM Customers; </div></code></pre> </div> <div class="text-center padding-10 margin-t-5">
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