scala> stagingDF.select("a_ingestion_dtm",unix_timestamp(col("a_ingestion_dtm"))).show(10,false)
  <console>:47: error: overloaded method value select with alternatives:
  (col: String,cols: String*)org.apache.spark.sql.DataFrame <and>
  (cols: org.apache.spark.sql.Column*)org.apache.spark.sql.DataFrame
  cannot be applied to (String, org.apache.spark.sql.Column)
          stagingDF.select("a_ingestion_dtm",unix_timestamp(col    ("a_ingestion_dtm"))).show(10,false)