Getting data as for alphanumeric values

Hi team,

I have created one flllat file Datastore objects, i have many fields one of them is SITE, the data type is varchar(4) and in the flat file i have data like 4002,4A02 etc..

For Alphanumeric site values , i am getting the values as <Null>  in the DS but for the number values i am getting the correct. Why it is behaving so ?

Please help me...

Regards,

Praveen.