星火数据框中小数精度

Question

我有一个数据帧：

val groupby = df.groupBy($"column1",$"Date")  
.agg(sum("amount").as("amount")) 
.orderBy($"column1",desc("cob_date")) 

当applyin窗函数添加新列差：

val windowspec= Window.partitionBy("column1").orderBy(desc("DATE")) 

groupby.withColumn("diffrence" ,lead($"amount", 1,0).over(windowspec)).show() 


+--------+------------+-----------+--------------------------+ 
| Column | Date  | Amount | Difference    | 
+--------+------------+-----------+--------------------------+ 
| A  | 3/31/2017 | 12345.45 | 3456.540000000000000000 | 
+--------+------------+-----------+--------------------------+ 
| A  | 2/28/2017 | 3456.54 | 34289.430000000000000000 | 
+--------+------------+-----------+--------------------------+ 
| A  | 1/31/2017 | 34289.43 | 45673.987000000000000000 | 
+--------+------------+-----------+--------------------------+ 
| A  | 12/31/2016 | 45673.987 | 0.00E+00     | 
+--------+------------+-----------+--------------------------+ 

我越来越小数与尾部零。当我做printSchema()获取数据类型的差异：decimal(38,18)。有人告诉我如何将数据类型更改为decimal(38,2)或删除尾随零

Answer 1

你可以像下面的具体小数的大小投的数据，

铅（$ “量”，1,0）.over（windowspec）.cast（DataTypes.createDecimalType（32,2））

Answer 2

在纯SQL中，可以使用公知技术：

SELECT ceil(100 * column_name_double)/100 AS cost ...