SQL 计算百分比

Question

我在一个表中有四列。

+------+-------+------------+---------------+
| Year | Month | OrderCount | SaleCount2015 |
+------+-------+------------+---------------+
| 2015 |   1   |    876     |     453       |
| 2015 |   2   |    764     |     548       |
| 2015 |   3   |    951     |     632       |
| 2015 |   4   |    ...     |     ...       |
+------+-------+------------+---------------+

我想计算每个月的 SalePercentage，但结果返回 0。 我使用以下 SQL 查询。

Select Year, 
       Month, 
       OrderCount, 
       SaleCount, 
       SaleCount/OrderCount AS SalePercentage
From TableName

谁能告诉我这个查询的问题？ 谢谢。

Answer 1

SELECT Year, Month, OrderCount, SaleCount,
    CAST (SaleCount AS FLOAT) / CAST(OrderCount AS FLOAT) AS SalePercentage
FROM TableName

您使用的是整数除法，因此5/10将是0 ，但5.0/10.0将是0.5

Answer 2

如果您使用的是sql server

如果你除以整数，那么你得到的结果是整数；

将一列或两列值转换为float或double

cast(SaleCount as float) /OrderCount AS SalePercentage

或者

(SaleCount*1.0)/OrderCount AS SalePercentage

最好检查OrderCount是否zero

case when OrderCount = 0 then 0
else (SaleCount*1.0)/OrderCount end AS SalePercentage 

演示sqlfiddle

Answer 3

使用Money类型进行财务计算...

SELECT Year, Month, OrderCount, SaleCount, IIF(OrderCount  = 0, 0, CAST(SaleCount AS MONEY)/CAST(OrderCount AS MONEY)) AS SalePercentage FROM TableName

Answer 4

无论您使用哪个数据库。 您的结果显示的不是百分比，而是一小部分。 如果您将其乘以 100，它将得到解决：

Select Year, 
       Month, 
       OrderCount, 
       SaleCount, 
       (SaleCount*100)/OrderCount AS SalePercentage
From TableName