Warring while finding Max, Min Date - Aggregator Stage

[K.A.R.PAULSON]

In a job I am trying to find out the maximum and minimum date from the given date field. For that I was made a job with Aggregator stage.
I am getting the required out put, but I am getting multiple warring in the log file. The warring message I am listed below.

Acc005_Aggr_MaxMinDate_TopAcc..Aggr_MaxMin_Date: At row 1991, link "Input_Agg", while processing column "Output_Agg.MIN_FIRST_SHIP_DATE"
Value treated as NULL
Attempt to convert String value "" to Long type unsuccessful


Please let me know how to handle this warring.

Thanks and regards
Regi

[T42]

Don't pass invalid data to the aggregator stage. Use a transformer's constraint. That's all.