with tmp as(
select SESSION_ID,PROCESS_ID,
case PROCESS_ID when 'STEP1' then 1
                when 'STEP2' then 2
                when 'STEP3' then 3
                when 'STEP4' then 4
                when 'STEP5' then 5 end as Step,
EX_TIMESTAMP
  from PROCESS_LOG),
tmp2 as(
select PROCESS_ID,Step,SESSION_ID,
Row_Number() over(partition by SESSION_ID order by EX_TIMESTAMP) as rn
  from tmp),
tmp3 as(
select PROCESS_ID,Step,
min(case when Step != rn then Step end) over(partition by SESSION_ID) as StopStep
  from tmp2)
select PROCESS_ID as PROCESS,count(*) as CNT
  from tmp3
 where StopStep is null or Step < StopStep
group by PROCESS_ID
order by PROCESS_ID