AWS Athena null values are replaced by N after table is created. How to keep them as it is?

问题

I'm creating a table in Athena from csv data in S3. The data has some columns quoted, so I use:

    ROW FORMAT SERDE 'org.apache.hadoop.hive.serde2.OpenCSVSerde'
WITH SERDEPROPERTIES (
  "separatorChar" = ",",
  'serialization.null.format' = '')

The serde works fine but then the null values in the resultant table are replaced with N. How can I keep the null values as empty or like Null etc, but not as N.
Thanks.

来源：https://stackoverflow.com/questions/61020631/aws-athena-null-values-are-replaced-by-n-after-table-is-created-how-to-keep-the