需求：员工id正常为8位，对于不满8位的员工id左侧用0补齐

import org.apache.spark.sql.{DataFrame, SparkSession}

object DataSetCreate {

  def main(args: Array[String]): Unit = {
    val spark = SparkSession
      .builder()
      .appName("test")
      .master("local[4]")
      .getOrCreate()
    import spark.implicits._

    val list = List(
      ("1001","zhangsan",10),
      ("44","zhang2",66),
      ("32432","zhang3",70),
      ("6757","zhang4",22),
      ("1","zhang4",22))
    val df: DataFrame = list.toDF("id","name","age")

    //需求：员工id正常为8位，对于不满8位的员工id左侧用0补齐
    //println(myLpad("h",8,"0"))
    spark.udf.register("xxx",myLpad _);
    df.selectExpr("xxx(id,8,'0') id","name","age").show()

    df.createOrReplaceTempView("data")
    spark.sql(
      """
        |select
        |xxx(id,8,'0') id,
        |name,
        |age
        |from data
        |""".stripMargin).show()

  }

    /**
     *
     * @param str 待补齐的字符串
     * @param len 最终补齐的长度
     * @param pad 使用pad填充
     * @return
     */
    def myLpad(str:String,len:Int,pad:String):String={
      //字符串长度
      val strLen: Int = str.length
      //需要补齐的长度
      val padLen: Int = len-strLen
      s"${pad * padLen}${str}"
    }

}