Need help with SQL for selecting ID where the sequence does not match..

Question

I have the following dilemma:
Database contains IDs as follows:
Incident#, Case#, & Part Sequence#
example
Record 1
Incident_Number = 123456
Case_Number = 1
Part_sequence = 1
Record 2
Incident_Number = 123456
Case_Number = 1
Part_sequence = 2
Sometimes the user will delete (let's say) Record 2 after creating a new Record 3
So now the sequencing goes as follows:
Record 1
Incident_Number = 123456
Case_Number = 1
Part_sequence = 1
Record 2
Incident_Number = 123456
Case_Number = 1
Part_sequence = 3
Now there will no longer be a Part_Sequence 2
Need a SQL to select all records where the maximum part sequence > than the count of Incident_number||'-'||Case_number
I tried the following:
select a.incident_number||'-'||a.case_number||'-'||a.part_sequence
from chsuser.a_compl_summary a
where a.entry_date >= '01-may-2011'
and max(a.part_sequence) > count(distinct a.incident_number||'-'||a.case_number)I end up getting a ORA-00934: group function is not allowed here (highlighting on the Max(a.part_sequence) portion.
Any suggestions/hints
Thanks

Answer 1

select  incident_number || '-' || case_number || '-' || part_sequence
  from  (
         select  incident_number,
                 case_number,
                 part_sequence,
                 max(part_sequence) over(partition by incident_number,case_number) max_seq,
                 count(*) over(partition by incident_number,case_number) cnt
           from  chsuser.a_compl_summary
           where entry_date >= DATE '2011-05-01'
  where cnt != max_seq
/SY.