30 lines
1.1 KiB
HTML
30 lines
1.1 KiB
HTML
<p>在项目中遇到要取两个表差集的情况</p>
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<p>假设有两个表tblNZPostCodes, NZPostcode 两个表中存储的都是新西兰的post code信息，字段一致，只是数据上有所差异。</p>
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<p> </p>
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<p>1. Union 获取两个表的合集并且自动过滤重复数据</p>
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<div class="cnblogs_code">
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<pre>Select * from tblNZPostCodes
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Union
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Select * from NZPostcode</pre>
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</div>
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<p>2. Union all 获取两个表的合集并且不过滤重复数据 </p>
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<div class="cnblogs_code">
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<pre>Select * from tblNZPostCodes
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Union all
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Select * from NZPostcode</pre>
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</div>
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<p>3. Intersect 获取两个表的交集</p>
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<div class="cnblogs_code">
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<pre>Select * from tblNZPostCodes
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intersect
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Select * from NZPostcode</pre>
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</div>
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<p>4. except 获取第1个表中存在，而第2个表中不存在的数据</p>
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<p> 比如，下面的语句将获取在tblNZPostCodes中存在，但NZPostcode中不存在的数据</p>
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<div class="cnblogs_code">
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<pre>Select * from tblNZPostCodes
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except
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Select * from NZPostcode</pre>
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</div>
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<p> </p>
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<p>转自：https://www.cnblogs.com/wphl-27/p/5488080.html</p> |