Maison >développement back-end >tutoriel php >mysql如何去除两个字段数据相同的记录?
比如说有个name列和一个eamil列,如果数据库里面有条记录的这两列的值相同(我说的是这条记录的对应的那两列的值相同,并不是同一条记录里面两列值相同)的话就自动删除其他多余的列而保留最新的那一条(也就是ID最小的那个,ID是一个自增主键)
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也就是说表里面有两条记录的name都是admin,email都是abc@163.com,我只想保留其中一条,这该怎么做
<code class="language-sql"><span class="k">delete</span> <span class="k">from</span> <span class="n">test</span> <span class="k">where</span> <span class="n">id</span> <span class="k">not</span> <span class="k">in</span><span class="p">(</span>
<span class="k">select</span> <span class="n">name</span><span class="p">,</span><span class="n">email</span><span class="p">,</span><span class="k">max</span><span class="p">(</span><span class="n">id</span><span class="p">)</span> <span class="k">from</span> <span class="n">test</span>
<span class="k">group</span> <span class="k">by</span> <span class="n">name</span><span class="p">,</span><span class="n">email</span> <span class="k">having</span> <span class="n">id</span> <span class="k">is</span> <span class="k">not</span> <span class="k">null</span><span class="p">)</span>
</code>
distinct
如果要保留id的最小值,例如: