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mysql-MySQL:多字段复合统计

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Release: 2016-06-06 09:35:50
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菜鸟求助:eves表中有三个国家字段,nat1, nat2, nat3,nat1为非空,其它两个不一定有数据。现在想统计3列中每个国家(包括出现在nat2和nat3里的国家)出现的次数,请问如何SELECT?感谢!!试过COUNT和GROUP BY,似乎无法实现啊……

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