Setting a NULL value in SSIS derived column

Ran into an interesting error while trying to set a null value to a column in a derived column task in SSIS.
Here is my statement:

[CustNum]=="" ? NULL(DT_STR, 4, 1252) : [CustNum]

And the error thrown:

For operands of the conditional operator, the data type DT_STR is supported only for input and cast operations.

The correct syntax for this is:

[CustNum]=="" ? (DT_STR, 4, 1252)NULL(DT_STR, 4, 1252) : [CustNum]

Not sure why this requires the explicit cast since you include the type in the null statement.

peace

 

 

My Z80 Homebrew Computer - The Pony80

 

 

 

 

SSIS Derived Column IIF/IF Expression

This is for my memory, but I figure if I have a hard time remembering, maybe someone else will...

For those of you who are trying to remember how to do IF/IIF functionality in the SSIS Derived Column control:

({comparison} ? {truepart} : {falsepart})

So, if I want to evaluate the similarity from a fuzzy lookup, it would look like this:

(_Similarity > .78 ? ID : "")

Maybe someday Microsoft will standardize all of the expression languages in their BI tools!

peace