How to De-Duplicate output rows



While creating a report, How do we De-Duplicate rows based on a $Field?

_fetch * from event group count_unique $Field1, $Field2, $Field3 limit 100

In the above query, the output will be generated with multiple rows having combinations of values from $Field1, Field2, $Field3. I want to De-Duplicate based on $Field1, such that, if a value has once appeared on $Field1, it should not create any other row.