在配置单元查询语言中将字符串列转换为3位数的比例

我有一个select语句如下

SELECT t5.Name AS ProductName
, CAST (t5.salerevenue AS DECIMAL(20,3)) AS Revenue
, CASE WHEN t5.PreviousRevenue <> 0 THEN CAST(t5.PresentRevenue/t5.PreviousRevenue*100 AS STRING)
       ELSE 'NA' 
       END AS RevenueTrend  

我想将RevenueTrend转换为小数点,最大刻度为3(20)。 123个 ) WHEN t5.PreviousRevenue <> 0 不见了,我得把它显示成“不”

我试着这样做

CASE WHEN t5.PreviousRevenue <> 0 THEN CAST((CAST(t5.PresentRevenue/t5.PreviousRevenue*100) AS DECIMAL(20,3)) AS STRING)
     ELSE 'NA' 
     END AS RevenueTrend    

但是我发现了一个语法错误。