When an user builds a report from "sc_task" table and includes "Business duration" field in the aggregation field. The generated report does not display any data for this field.While this works fine for another report that is generated from 'incident' table which has same configuration as the one build on "sc_task" table.
Both the reports have same filtering conditions defined on them, but "incident" table does contain records that matches this condition where records had "Business duration" with non-empty values where as "sc_task" table contain records that matches this condition but all those records had no value for "Business duration" field.
It is behaving as expected. The reason why the data is not getting displayed in the report generated on 'sc_task' is that records returned after the condition is applied did not have any value for "Business duration" field. After changing the condition the report did display the data as expected as those returned records had data in them.