Removing duplicates from a report
I have a file which contains a list of services provided by teachers. Each record contains date , time, teachers name, customer name and service type. Some services are private lessons and some are group training sessions.
I am trying to produce a list of services given by a particular teacher but I want to list only one line in the case the service is a group, because I am interested in knowing how many sessions the teacher taught not how many students were taught.
How can I write a script to exclude all duplicates except one of each (duplicates identified by date+time+teachers name)