WITH RankedProcesses AS (
  SELECT
    SESSION_ID,
    PROCESS_ID,
    ROW_NUMBER() OVER (PARTITION BY SESSION_ID ORDER BY EX_TIMESTAMP) AS StepRank
  FROM PROCESS_LOG
  WHERE EX_TIMESTAMP = (SELECT MIN(EX_TIMESTAMP) FROM PROCESS_LOG WHERE SESSION_ID = SESSION_ID)
)
SELECT
  SESSION_ID,
  SUM(CASE WHEN StepRank = 1 THEN 1 ELSE 0 END) AS STEP1_COUNT,
  SUM(CASE WHEN StepRank = 2 THEN 1 ELSE 0 END) AS STEP2_COUNT,
  SUM(CASE WHEN StepRank = 3 THEN 1 ELSE 0 END) AS STEP3_COUNT,
  SUM(CASE WHEN StepRank = 4 THEN 1 ELSE 0 END) AS STEP4_COUNT,
  SUM(CASE WHEN StepRank = 5 THEN 1 ELSE 0 END) AS STEP5_COUNT
FROM RankedProcesses
GROUP BY SESSION_ID;