我有一個超過 100 列的 DataFrame。我想將一些列移到 DataFrame 的最左側。有沒有一種簡單的方法來指定我想向左移動哪些列，然后其余列保持相同的順序？我知道我可以select用來重新排序列，但鑒于我有超過 100 列，我想避免這種情況。
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import org.apache.spark.sql.types.StructType
import org.apache.spark.sql.{Encoders, SparkSession}
import spark.implicits._
case class D(
C1: String,
C2: String,
C3: String,
C4: String,
C5: String,
C6: String,
C7: String,
C8: String,
C9: String,
C10: String
)
val schema: StructType = Encoders.product[D].schema
val fields = schema.fieldNames
// or fields = DataFrame.columns ...
val source = Seq(
D("1", "1", "1", "1", "1", "1", "1", "1", "1", "1"),
D("2", "2", "2", "2", "2", "2", "2", "2", "2", "2"),
D("3", "3", "3", "3", "3", "3", "3", "3", "3", "3")
).toDF()
source.printSchema()
// root
// |-- C1: string (nullable = true)
// |-- C2: string (nullable = true)
// |-- C3: string (nullable = true)
// |-- C4: string (nullable = true)
// |-- C5: string (nullable = true)
// |-- C6: string (nullable = true)
// |-- C7: string (nullable = true)
// |-- C8: string (nullable = true)
// |-- C9: string (nullable = true)
// |-- C10: string (nullable = true)
source.show()
// --- --- --- --- --- --- --- --- --- ---
// | C1| C2| C3| C4| C5| C6| C7| C8| C9|C10|
// --- --- --- --- --- --- --- --- --- ---
// | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|
// | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|
// | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|
// --- --- --- --- --- --- --- --- --- ---
val colFirst = Array("C1", "C2", "C10", "C7")
val tmpLast = fields.diff(colFirst)
val cols = colFirst tmpLast
val res1 = source.select(cols.head, cols.tail:_*)
res1.printSchema()
// root
// |-- C1: string (nullable = true)
// |-- C2: string (nullable = true)
// |-- C10: string (nullable = true)
// |-- C7: string (nullable = true)
// |-- C3: string (nullable = true)
// |-- C4: string (nullable = true)
// |-- C5: string (nullable = true)
// |-- C6: string (nullable = true)
// |-- C8: string (nullable = true)
// |-- C9: string (nullable = true)
res1.show(false)
// --- --- --- --- --- --- --- --- --- ---
// |C1 |C2 |C10|C7 |C3 |C4 |C5 |C6 |C8 |C9 |
// --- --- --- --- --- --- --- --- --- ---
// |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
// |2 |2 |2 |2 |2 |2 |2 |2 |2 |2 |
// |3 |3 |3 |3 |3 |3 |3 |3 |3 |3 |
// --- --- --- --- --- --- --- --- --- ---
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