Null value error

Start your custom column with if [Days] = null then null else if ..../your code/... [Days] < 2...

You can find how to use coalesce operator here.

So, I was unable to replace values, as it asks to insert a date value. Even with my column categorized as ABC123 he didn't allow it.

My intention is to leave the result blank or empty if it is null.

Another way I tried to do it using se:

At first it works.

However, when I categorize the column for date, it becomes null again

hudsonvj You said you were doing a merge with another table. So, parent A table merged with child B table, yes?

Why not do these transformations in the detail table first, then merge the tables together? 

If you need a value from parent A table to do this child B table transformation, you can always create a reference version of parent A table, call it Clone table. The Clone table would only contain the columns needed to merge with child B table and whatever columns you need to do this transformation.

So merge child B table with Clone and do your date math. There shouldn't be any null dates then hopefully. 

Once completed, then you merge parent A table with the now transformed child B table as you were doing before,. Now when you expand, your transformations were already done. No need to worry with any nulls.

You can also deactivate the Clone table since it should never be used but it will be executed when merged with child B table. 

Hopefully this makes sense. I've had to do this before and it was simpler to do this and maintain it over time than  it is to figure out a really convoluted if then nesting logic. 

--Treb