SQL：如何使用GROUP BY得到加權計數？

Question

我怎麼能做出這樣的查詢：

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

但是，在freq總和值從weight柱代替數數每排爲1？

我正在使用MySQL 5.1。

Answer 1

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

Answer 2

您想使用Sum集合函數來處理這個問題。

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

應該訣竅！

Answer 3

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

Answer 4

使用sum(weight) as freq在您選擇查詢