Hi SyedF,
When you add an expression (ISNULL( [alpha_desc] )?[determinant_value]: [alpha_desc])in Derived Column Transformation, you receive the error message The data types "DT_R8" and "DT_WSTR" are incompatible for the conditional operator.
After testing the issue in my environment, I can reproduce it.
As per my understanding, the issue should be caused by the following reason: the [determinant_value] column with DT_R8 data type, while [alpha_desc] column with DT_WSTR data type. The data types "DT_R8" and "DT_WSTR" are incompatible
for the conditional operator.
So to fix this issue, please change the original expression to like below based on your requirement:
The derived column uses DT_R8 data type:
ISNULL( [alpha_desc] ?[determinant_value]: (DT_R8)[alpha_desc]
The derived column uses DT_WSTR data type:
ISNULL( [alpha_desc] ? (DT_WSTR,50)[determinant_value]: [alpha_desc]
If there are any other questions, please feel free to ask.
Thanks,
Katherine Xiong