SELECT PROCESS_ID AS PROCESS,
       SUM(CNT) AS CNT
  FROM (SELECT SESSION_ID, 
               PROCESS_ID,
               USER_ID,
               EX_TIMESTAMP,
               CASE
                 WHEN PROCESS_ID = 'STEP1' THEN '1'
                 WHEN PROCESS_ID = 'STEP2' AND LAG(PROCESS_ID, 1) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP1' THEN '1'
                 WHEN PROCESS_ID = 'STEP3' AND LAG(PROCESS_ID, 1) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP2' AND LAG(PROCESS_ID, 2) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP1' THEN '1'
                 WHEN PROCESS_ID = 'STEP4' AND LAG(PROCESS_ID, 1) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP3' AND LAG(PROCESS_ID, 2) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP2' AND LAG(PROCESS_ID, 3) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP1' THEN '1'
                 WHEN PROCESS_ID = 'STEP5' AND LAG(PROCESS_ID, 1) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP4' AND LAG(PROCESS_ID, 2) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP3' AND LAG(PROCESS_ID, 3) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP2' AND LAG(PROCESS_ID, 4) over (PARTITION BY SESSION_ID ORDER BY SESSION_ID,EX_TIMESTAMP) = 'STEP1' THEN '1'
                 ELSE '0'
               END AS CNT
          FROM PROCESS_LOG
         ORDER BY SESSION_ID,
                  EX_TIMESTAMP   
        )
 GROUP BY PROCESS_ID
 ORDER BY PROCESS_ID