如何使用Oracle SQL对每个组中的第一个和最后一个记录进行组记录和计算?

I have a table in Oracle 10g DB engine that contains records of service operations. The requirement is to calculate the processing time of each service request. Each service request may generate multiple records each representing a step in the process. So I have a table with the following columns:I have a table in Oracle 10g DB engine that con