Отдельный A.ecode_id напрямую управляется группой с помощью
SELECT A.ecode_id
, SUM(C.eligible_2018) monthlyBudgetAmt
FROM vefm_dailybudget A
JOIN vefm_comp_division B ON B.id = A.division
JOIN vefm_engineer_details C ON A.ecode_id=C.ecode
LEFT JOIN vefm_user F ON A.approved_by=F.ecode
JOIN vefm_region D ON A.region=D.id
WHERE A.approval_amount != 0
AND A.division=1
AND date(A.approval_date)
BETWEEN '2018-04-01' AND '2018-04-30'
AND A.budget_type='monthly'
GROUP BY A.ecode_id
, если вам нужна общая сумма для отличного результата, вы можете попробовать
SELECT SUM( t.monthlyBudgetAmt )
FROM (
SELECT DISTINCT A.ecode_id
,C.eligible_2018 AS monthlyBudgetAmt
FROM vefm_dailybudget AS A
JOIN vefm_comp_division AS B ON (B.id = A.division)
JOIN vefm_engineer_details AS C ON (A.ecode_id=C.ecode)
LEFT JOIN vefm_user AS F ON (A.approved_by=F.ecode)
JOIN vefm_region AS D ON (A.region=D.id)
WHERE A.approval_amount != 0
AND A.division=1
AND date(A.approval_date) BETWEEN '2018-04-01' AND '2018-04-30'
AND A.budget_type='monthly' GROUP BY A.ecode_id
)