Calculate SUM of a particular column in Crystal Report in ASP.Net

Convert the Datatype of Amount column into an integer type and check with database again. In crystal reports the sum will appear only to the number fields and as your post says the Maximum, Minimum, Count, Distinct count, Nth Largest, Nth Smallest will comes only for varchars.

Ref:

http://stackoverflow.com/questions/7316552/running-total-field-gives-options-for-min-max-etc-but-not-sum