如何将列中的所有值与 SUM() 等 SQL 相乘
假设我有这样的 1 列表格:
Lets say I have table with 1 column like this:
Col A
1
2
3
4
如果我 SUM 它，那么我会得到这个:
If I SUM it, then I will get this:
Col A
10
我的问题是:如何将 Col A 相乘才能得到以下结果?
My question is: how do I multiply Col A so I get the following?
Col A
24
推荐答案
结合使用ROUND、EXP、SUM和日志
SELECT ROUND(EXP(SUM(LOG([Col A]))),1)
FROM yourtable
SQL 小提琴:http://sqlfiddle.com/#!3/d43c8/2/0
解释
LOG 返回 col a ex 的对数.LOG([Col A]) 返回
LOG returns the logarithm of col a ex. LOG([Col A]) which returns
0
0.6931471805599453
1.0986122886681098
1.3862943611198906
然后您使用 SUM 将它们全部加在一起 SUM(LOG([Col A])) 返回
Then you use SUM to Add them all together SUM(LOG([Col A])) which returns
3.1780538303479453
然后使用返回的 EXP(SUM(LOG(['3.1780538303479453']))) 计算该结果的指数
Then the exponential of that result is calculated using EXP(SUM(LOG(['3.1780538303479453']))) which returns
23.999999999999993
然后最后使用 ROUND ROUND(EXP(SUM(LOG('23.9999999999999993'))),1) 进行四舍五入得到 24
Then this is finally rounded using ROUND ROUND(EXP(SUM(LOG('23.999999999999993'))),1) to get 24
简单的解决方法:
发生了无效的浮点运算.
An invalid floating point operation occurred.
当您的数据中有 0 时
SELECT ROUND(EXP(SUM(LOG([Col A]))),1)
FROM yourtable
WHERE [Col A] != 0
如果你只有 0 那么上面会给出 NULL 的结果.
If you only have 0 Then the above would give a result of NULL.
当您的数据集中有负数时.
When you have negative numbers in your data set.
SELECT (ROUND(exp(SUM(log(CASE WHEN[Col A]<0 THEN [Col A]*-1 ELSE [Col A] END))),1)) *
(CASE (SUM(CASE WHEN [Col A] < 0 THEN 1 ELSE 0 END) %2) WHEN 1 THEN -1 WHEN 0 THEN 1 END) AS [Col A Multi]
FROM yourtable
示例输入:
1
2
3
-4
输出:
Col A Multi
-24
SQL 小提琴:http://sqlfiddle.com/#!3/01ddc/3/0
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