Scala：如何组合两个数据框？

Question

第一个 Df 是：

ID Name ID2 Marks
1   12    1   333

第二个 Df2 是：

ID Name ID2 Marks
1         3   989
7   98    8   878

我需要的输出是：

ID Name ID2 Marks
1   12    1   333
1         3   989
7   98    8   878

请帮助！

Answer 1

用途union或unionAll功能：

df1.unionAll(df2)
df1.union(df2)

例如：

scala> val a = (1,"12",1,333)
a: (Int, String, Int, Int) = (1,12,1,333)

scala> val b = (1,"",3,989)
b: (Int, String, Int, Int) = (1,"",3,989)

scala> val c = (7,"98",8,878)
c: (Int, String, Int, Int) = (7,98,8,878)

scala> import spark.implicits._
import spark.implicits._

scala> val df1 = List(a).toDF("ID","Name","ID2","Marks")
df1: org.apache.spark.sql.DataFrame = [ID: int, Name: string ... 2 more fields]

scala> val df2 = List(b, c).toDF("ID","Name","ID2","Marks")
df2: org.apache.spark.sql.DataFrame = [ID: int, Name: string ... 2 more fields]

scala> df1.show
+---+----+---+-----+
| ID|Name|ID2|Marks|
+---+----+---+-----+
|  1|  12|  1|  333|
+---+----+---+-----+


scala> df2.show
+---+----+---+-----+
| ID|Name|ID2|Marks|
+---+----+---+-----+
|  1|    |  3|  989|
|  7|  98|  8|  878|
+---+----+---+-----+


scala> df1.union(df2).show
+---+----+---+-----+
| ID|Name|ID2|Marks|
+---+----+---+-----+
|  1|  12|  1|  333|
|  1|    |  3|  989|
|  7|  98|  8|  878|
+---+----+---+-----+