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,
Row_Number() over(partition by SESSION_ID order by EX_TIMESTAMP) as rn
  from PROCESS_LOG),
rec(SESSION_ID,PROCESS_ID,Step,rn) as(
select SESSION_ID,PROCESS_ID,Step,rn
  from tmp
 where Step = 1 and rn = 1
union all
select b.SESSION_ID,b.PROCESS_ID,b.Step,b.rn
  from rec a
  Join tmp b
    on b.SESSION_ID = a.SESSION_ID
   and b.Step = a.Step+1
   and b.rn = a.rn+1)
select PROCESS_ID as PROCESS , count(*) as CNT
  from rec
group by PROCESS_ID
order by PROCESS_ID