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25 lines
2.8 KiB
HTML
25 lines
2.8 KiB
HTML
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<h1>SQL RIGHT JOIN 关键字</h1>
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<h2>SQL RIGHT JOIN 关键字</h2> <p>RIGHT JOIN 关键字从右表（table2）返回所有的行，即使左表（table1）中没有匹配。如果左表中没有匹配，则结果为 NULL。</p> <h3>SQL RIGHT JOIN 语法</h3> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT <em>column_name(s)</em><br/> FROM <em>table1</em><br/> RIGHT JOIN <em>table2</em><br/> ON <em>table1.column_name</em>=<em>table2.column_name</em>;</div></code></pre></div> <p>或：</p> <div class="code notranslate"><pre><code class="language-sql"><div> SELECT <em>column_name(s)</em><br/> FROM <em>table1</em><br/> RIGHT OUTER JOIN <em>table2</em><br/> ON <em>table1.column_name</em>=<em>table2.column_name</em>;</div></code></pre></div> <p><b>注释：</b>在某些数据库中，RIGHT JOIN 称为 RIGHT OUTER JOIN。</p> <p style="text-align:center"><img alt="SQL RIGHT JOIN" height="145" src="../image/5615cc0991a29.gif" width="200"/></p> <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 "Orders" 表的数据：</p> <table class="reference notranslate">
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<tr>
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<th width="15%">OrderID</th> <th>CustomerID</th> <th>EmployeeID</th> <th>OrderDate</th> <th>ShipperID</th> </tr>
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<tr>
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<td>10308</td> <td>2</td> <td>7</td> <td>1996-09-18</td> <td>3</td> </tr>
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<tr>
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<td>10309</td> <td>37</td> <td>3</td> <td>1996-09-19</td> <td>1</td> </tr>
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<td>10310</td> <td>77</td> <td>8</td> <td>1996-09-20</td> <td>2</td> </tr>
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</table>
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<p>选自 "Employees" 表的数据：</p> <table class="reference notranslate">
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<tr>
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<th>EmployeeID</th> <th>LastName</th> <th>FirstName</th> <th>BirthDate</th> <th>Photo</th> <th>Notes</th> </tr>
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<tr>
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<td>1</td> <td>Davolio</td> <td>Nancy</td> <td>12/8/1968</td> <td>EmpID1.pic</td> <td>Education includes a BA in psychology.....</td> </tr>
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<tr>
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<td>2</td> <td>Fuller</td> <td>Andrew</td> <td>2/19/1952</td> <td>EmpID2.pic</td> <td>Andrew received his BTS commercial and....</td> </tr>
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<tr>
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<td>3</td> <td>Leverling</td> <td>Janet</td> <td>8/30/1963</td> <td>EmpID3.pic</td> <td>Janet has a BS degree in chemistry....</td> </tr>
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</table>
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<h2>SQL RIGHT JOIN 实例</h2> <p>下面的 SQL 语句将返回所有员工及他们处理的订单：</p> <div class="example margin-b-10"> <h2 class="example">实例</h2> <pre><code class="language-sql"><div class="example_code notranslate"> SELECT Orders.OrderID, Employees.FirstName<br/>FROM Orders<br/>RIGHT JOIN Employees<br/>ON Orders.EmployeeID=Employees.EmployeeID<br/>ORDER BY Orders.OrderID;</div></code></pre> </div> <p><strong>注释：</strong>RIGHT JOIN 关键字从右表（Employees）返回所有的行，即使左表（Orders）中没有匹配。</p> <br/><div class="text-center padding-10 margin-t-5">
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