Not sure if I got your question correctly. Can you please explain little bit what you are trying to achieve?
Please note NULL and Blank values are not same although they look similar. You have to see your underlying data and see what is the default value for that column. You can use the SQLs below.
SELECT *
FROM "SYS"."TABLE_COLUMNS"
WHERE "SCHEMA_NAME" = <'YOUR_SCHEMA'> AND IS_NULLABLE = 'TRUE'.
SELECT *
FROM "SYS"."TABLE_COLUMNS"
WHERE "SCHEMA_NAME" = <'YOUR_SCHEMA'> AND IS_NULLABLE = 'FALSE' .
Notice the change in DEFAULT_VALUE Column for the above statements .
You can also add TABLE_NAME in your Where clause to further restrict the data set.
Cheers
Anindya
