how to convert date of format string to timestamp in spark?

%scala
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.functions.{col, to_date}

Seq(("20110813"),("20090724")).toDF("Date").select(
col("Date"),
to_date(col("Date"),"yyyy-mm-dd").as("to_date")
).show()

+--------+-------+
|    Date|to_date|
+--------+-------+
|20110813|   null|
|20090724|   null|
+--------+-------+
+--------+----------+
|    Date|   to_date|
+--------+----------+
|20110813|2011-01-13|
|20090724|2009-01-24|
+--------+----------+
Seq(("20110813"),("20090724")).toDF("Date").select(
col("Date"),
to_date(col("Date"),"yyyymmdd").as("to_date")
).show()

I am trying to convert a string to timestamp, but I am getting always null/default values returned to the date value

>Solution :

You haven’t given value for the new column to convert. you should use withColumn to add the new date column and tell him to use Date column values.

val df = Seq(("20110813"),("20090724")).toDF("Date")
val newDf = df.withColumn("to_date", to_date(col("Date"), "yyyy-MM-dd"))
newDf.show()