相关疑难解决方法(0)

我刚起步，我有数据框df：

+----------+------------+-----------+
| Column1  | Column2    | Sub       |                          
+----------+------------+-----------+
| 1        | 2          | 1         |                                         
+----------+------------+-----------+
| 4        | null       | null      |                          
+----------+------------+-----------+
| 5        | null       | null      |                          
+----------+------------+-----------+
| 6        | 8          | 2         |                          
+----------+------------+-----------+

当减去两列时，一列为null，因此结果列也为null。

df.withColumn("Sub", col(A)-col(B))

预期输出应为：

+----------+------------+-----------+
|  Column1 | Column2    | Sub       |                          
+----------+------------+-----------+
| 1        | 2          | 1         |                                           
+----------+------------+-----------+
| 4        | null       | 4         |                          
+----------+------------+-----------+
| 5        | null       | 5         |                          
+----------+------------+-----------+
| …