with history AS
            (
            select
                 session_id 
                ,lag(process_id) OVER (partition by session_id order by ex_timestamp) bef
                ,process_id 
                ,lead(process_id, 1) OVER (partition by session_id order by ex_timestamp) P2
                ,lead(process_id, 2) OVER (partition by session_id order by ex_timestamp) P3
                ,lead(process_id, 3) OVER (partition by session_id order by ex_timestamp) P4
                ,lead(process_id, 4) OVER (partition by session_id order by ex_timestamp) P5
            from
                process_log
            group by 
                session_id, process_id
            ), result as (
            select process_id PROCESS, count(*) CNT FROM history where bef is null AND  process_id = 'STEP1'
            UNION ALL
            select P2 PROCESS, count(*) CNT FROM history where bef is null AND process_id = 'STEP1' AND P2 = 'STEP2'
            UNION ALL
            select P3 PROCESS, count(*) CNT FROM history where bef is null AND process_id = 'STEP1' AND P2 = 'STEP2' AND P3 = 'STEP3'
            UNION ALL
            select P4 PROCESS, count(*) CNT FROM history where bef is null AND process_id = 'STEP1' AND P2 = 'STEP2' AND P3 = 'STEP3' AND P4 = 'STEP4'
            UNION ALL
            select P5 PROCESS, count(*) CNT FROM history where bef is null AND process_id = 'STEP1' AND P2 = 'STEP2' AND P3 = 'STEP3' AND P4 = 'STEP4' AND P5 = 'STEP5'
            ) 
            select PROCESS, CNT FROM result where process is not null  order by 1
            ;