SQL：如何使用 GROUP BY 获得加权计数？

Question

我如何进行如下查询：

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

但是其中 freq 对 weight 列中的值进行求和，而不是将每一行计为 1？

我正在使用 MySQL 5.1。

Answer 1

您想使用 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

在选择查询中使用 sum(weight) as freq