Oracle cumulative count using SYS_CONNECT_BY_PATH

Question

When i have tried the below query on actual data it returned more number of records. Please help to resolve this issue.

Below is the actual data in table DM_TEMP_SUM

Answer 1

Solely with a trial and error over your SQL Fiddle sample data, this is the query returning your expected data:

SELECT SYS_CONNECT_BY_PATH(firmware_version, '/') path_,
  firmware_version,
  device_count,
  dmc_id,
  charging_group_id,
  IMAGE_PREREQUISITE,
  (SELECT SUM(device_count)
  FROM DM_TEMP_SUMMING_DVC_BY_FW t2
  START WITH t1.firmware_version = t2.firmware_version
        and T1.dmc_id = T2.dmc_id
        and T1.charging_group_id = T2.charging_group_id
  CONNECT BY nocycle PRIOR firmware_version=image_prerequisite and prior dmc_id = dmc_id and prior charging_group_id = charging_group_id
  ) sum_device
FROM DM_TEMP_SUMMING_DVC_BY_FW t1
START WITH image_prerequisite IS NULL
CONNECT BY nocycle PRIOR firmware_version = image_prerequisite
    and prior dmc_id = dmc_id
    and prior charging_group_id = charging_group_id

Note: Yes, the charging_group_id and dmc_id are very important for your expected result, as krokodilko correctly mentioned in his above comment.