scala spark选择并添加带有别名的列
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spark select and add columns with alias
提问by katty
I want to select few columns, add few columns or divide, with some columns as space padded and store them with new names as alias. For example in SQL should be something like:
我想选择几列，添加几列或分隔，将一些列作为空格填充并使用新名称作为别名存储它们。例如在 SQL 中应该是这样的：
select " " as col1, b as b1, c+d as e from table
How can I achieve this in Spark?
如何在 Spark 中实现这一目标？
回答by pheeleeppoo
You can also use the native DF functions as well. For example given:
您也可以使用本机 DF 函数。例如给出：
import org.apache.spark.sql.functions._
val df1 = Seq(
("A",1,5,3),
("B",3,4,2),
("C",4,6,3),
("D",5,9,1)).toDF("a","b","c","d")
select the columns as:
选择列为：
df1.select(lit(" ").as("col1"),
col("b").as("b1"),
(col("c") + col("d")).as("e"))
gives you the expected result:
给你预期的结果：
+----+---+---+
|col1| b1| e|
+----+---+---+
| | 1| 8|
| | 3| 6|
| | 4| 9|
| | 5| 10|
+----+---+---+
回答by Karthick
with Spark-SQL, you can do the same way.
使用 Spark-SQL，您也可以这样做。
import org.apache.spark.sql.functions._
val df1 = Seq(
("A",1,5,3),
("B",3,4,2),
("C",4,6,3),
("D",5,9,1)).toDF("a","b","c","d")
df1.createOrReplaceTempView("table")
df1.show()
val df2 = spark.sql("select ' ' as col1, b as b1, c+d as e from table ").show()
Input:
输入：
+---+---+---+---+
| a| b| c| d|
+---+---+---+---+
| A| 1| 5| 3|
| B| 3| 4| 2|
| C| 4| 6| 3|
| D| 5| 9| 1|
+---+---+---+---+
Output :
输出 ：
+----+---+---+
|col1| b1| e|
+----+---+---+
| | 1| 8|
| | 3| 6|
| | 4| 9|
| | 5| 10|
+----+---+---+
