SELECT
t.id as task_id,
GROUP_CONCAT(DISTINCT tf.id) as task_files_id,
GROUP_CONCAT(DISTINCT tf.filename) as task_files_filename, 
GROUP_CONCAT(DISTINCT  st.id) as subtask_id,
GROUP_CONCAT(DISTINCT stf.filename) as subtask_file_filename
FROM tasks t
LEFT JOIN task_files tf ON tf.task_id= t.id
LEFT JOIN sub_tasks st ON st.task_id= t.id
LEFT JOIN sub_task_files stf ON stf.sub_task_id= st.id
WHERE t.id=149 and t.company_id=1;