SQL：如何使用GROUP BY获得加权计数？

Question

如何进行如下查询：

select myvalue, count() as freq from mytable group by myvalue;

但是freq对weight列的值求和而不是将每行计为1？

我正在使用MySQL 5.1。

Answer 1

您希望使用Sum聚合函数来处理此问题。

SELECT MyValue, Sum(weight) AS Total
FROM mytable
GROUP BY myvalue;

应该做的伎俩！

Answer 2

select myvalue, sum(weight) as freq from mytable group by myvalue;

Answer 3

select myvalue, SUM(weight) as freq from mytable group by myvalue;

Answer 4

在您的选择查询中使用sum(weight) as freq