Need help narrowing down to unique record when unexpected duplicates.

[FerdH4]

Good Day Cognos Experts,

I have a table which (thank goodness) has a unique key but appears that logical duplicates are being created in that table in error by the source program.  The downstream result is in the Report output I'm getting duplicate rows in my report because of later Joins I must do using either Study ID or Exam Number.

The three most relevant fields in this table are:
1. Study ID (by design almost unique)
2. Exam Number (no design intent to be unique)
3. Event Log ID (actual internally sequentially assigned key to the table and thus always unique). 

Offending records in this table look like this:
Study ID   Exam Number       Event Log ID
3261991    00000XR260044096  608448
3261991    00000XR260044096  608449

As shown above I've got two records where 100% of the data is identical except for the Event Log ID value.  I only want my Query to output a single occurrence of what appears to be duplicate records.  If I had a choice,  I think I'd prefer to use the "first" record.   

What can I do within the confines of my Query to focus the attention on just one of these two duplicates? 

I've tried adding "Minimum" to the left of the field Expression Definition like Minimum([Event Log ID]) but that didn't make any difference.  Maybe I've used that expression wrongly.

Thanks for sharing hints with me.