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请教一个sql 问题列如表A有四个字段f1,f2,f3,f4，我要获得分组统计数据当f1='a'时，select f1,f2,count(1) from A group by f1,f2当f1='b'时，select f1,f3,count(1) from A group by f1,f3当f1='c'时，select f1,f4,count(1) from A group by f1,f4这可以在一个语句中写出来吗？除了union的方式数据库环境：mysql
see: http://sqlfiddle.com/#!9/241bf6/5
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see: http://sqlfiddle.com/#!9/241bf6/5