Want to differentiate whether a file contains all null values in particular column or only null values in few rows.

Hello all,

I had one file which contains some null values and some state values. So in that case I am using the tester to filter null and non null values .but another file contains all the null values in the same column.so in the both cases we are getting the output in failed port as both files contains​ some null values. So how to differentiate whether a particular file contains all null values in the column or only few null values. So that if file contains all null values then we can send the error message.