Here are the conditions

# a daily download from a mainframe populates this table, "sourcedataset", with columns c1, c2, c3... c10 - the primary key is c1
# you've got a table in this database called "targetdataset" with columns c1, c2, c3... c14 - the primary key is c1
# you need to determine

* which rows in targetdataset need to be updated,
* which rows in targetdataset need to be deleted,
* which rows in sourcedataset need to be added to targetdataset

# users have r/w access to targetdataset's columns c11, c12, c13, c14, so this process should not touch the user's data

Honestly, i am bit puzzled. Can you pls give me any hints?