I SELECTing records in a table, but don't know how to get what I want. Here's what I am SELECTing:

Field1 Field2 Field3 Field4
100 A
100 A A A
200 A
200 A A A
300 A
300 A A A
300 A B B
400 A
500 A
500 A A A

I want to discard all records that are EMPTY(Field3) AND
EMPTY(Field4) AND also have a duplicate number in Field1 like where Field1 = 100 and Field1 = 200 and Field1 = 300 and Field1 = 500. The first record of all those sets of records would be discarded. I would only SELECT all the records after the first record of those sets.
But I don't want to discard any records where Field 1 does not have a duplicate number in Field1 like where Field1 = 400. I would want to select the one and only record for Field1 = 400.

So the result of my SELECT would be:

Field1 Field2 Field3 Field4
100 A A A
200 A A A
300 A A A
300 A B B
400 A
500 A A A

How can I do this with a SELECT? TIA