I’m working on a data quality workflow where I validate incoming records for null or missing values.
Even when a column clearly contains nulls, my rule doesn’t trigger and the record passes validation.

Here’s the logic I’m using:

CASE
WHEN column_name IS NULL THEN 'FAIL'
ELSE 'PASS'
END
But NULL records still return PASS.

Things I’ve checked:

• The column datatype is VARCHAR

• The source file is CSV

• Some values look empty ("") but not sure if they are treated as NULL

• My questions:

  1. Is there a difference between empty string and NULL in SQL during validation?

  2. How can I reliably detect actual NULL vs whitespace vs empty string?