>>>

>>>PartId     PartNo  SerialNo     Sequence
>>>1          AS345   ANB-121             1
>>>2          AS345   ANB-122             2
>>>3          AS345   ANB-123             3
>>>4          AS345   ANB-124             4
>>>5          A34SF   1212544             1
>>>6          B21AC   ANB-A1              1
>>>7          B21AC   ANB-A2              2
>>>8          ANG34   ANG34               1
>>>

>>>
>>>From the above set the query should return rows 5 and 8 because those partnumber/serialno combinations only appear once.
>>
>>But they are all unique?
>>What makes rows 5 and 8 different?
>>Maybe because there is no other rows with the same PartNo?
>
>It looks like they have some common part of SerialNo, such as ANB-

Yep, but that doesn't make them equal :-)