Crystal Reports, Sum of DateTime field, and group by User

I want to开发者_如何学Python calculate sum of field (DateTime) in Crystal Reports , and for each group.

When i right click in field then Insert->Smmary ,in this window i can select group and it is ok. Also I can select Summary (Minimum, Maximum,Count...) BUT no SUM , why?

The reason (as Arvo implies) is that there is no sense in which datetimes can be added to each other.

You can create a crystal formula to derive the number of seconds since midnight in a datetime field - this would look like:

Hour ({MyTable.MyDate}) * 3600 + 
Minute ({MyTable.MyDate}) * 60 + 
Second ({MyTable.MyDate})

(Crystal's DateTime functions can be found in the Function Tree in the Formula Editor dialog, under the Date and Time option.)

The formula field could then be SUMmed like any other numeric field - the result would be expressed in seconds.

EDIT:

Assuming there are no padding characters in l1, a formula item with the expression:

ToNumber (Left (DefaultReportPlugin_DetailedDailyReport_ReportData.I1, 2)) * 60 +
ToNumber (Right (DefaultReportPlugin_DetailedDailyReport_ReportData.I1, 2)) 

would convert the string to a number expressed in minutes. (The Left, Right and ToNumber fields can be found under the Strings option in the Function Tree in the Formula Editor dialog.)

A sum of the formula (expressed in minutes) can be displayed by inserting the formula item into the report, right-clicking on it and selecting the Insert > Summary... option from the dropdown menu.