ORA-00979: not a GROUP BY expression

 SELECT 
proj.name,
proj.area,
proj.position,
proj.num AS houseCount, 
proj.buildingArea,
proj.planStartDate, 
CASE WHEN proj.rate = '100%' THEN TO_CHAR(proj.modifyTime, 'YYYY-MM-DD HH24:MI:SS') ELSE proj.planEndDate END AS builtTime,
CASE WHEN proj.rate = '100%' THEN '已竣工' ELSE '未竣工' END AS built,
'公租房' AS type,
count(h.ID) - count(t.houseID) AS unallotted,
min(t.addTime) allotTime, 
count(t.houseID) AS allotted, 
sum(t.JTRS) AS amount,
sum(CASE WHEN t.type = 1 THEN 1 ELSE 0 END) AS lowIncome,
sum(CASE WHEN t.type = 2 THEN 1 ELSE 0 END) AS newToWork, 
sum(CASE WHEN t.type = 3 THEN 1 ELSE 0 END) AS otherCity,
sum(CASE WHEN t.type = 4 THEN 1 ELSE 0 END) AS unitApply 

FROM projectplan proj 
INNER JOIN houses h ON h.projectId = proj.id 
LEFT JOIN (SELECT a.type, map.addTime, map.houseID, f.JTRS
FROM tenanthousemapping map, tenant t, accessapply a, familyinfo f 
WHERE t.ID = map.tenantID AND f.UserId = t.ID AND t.ApplyID = a.id AND map.status = 1) t 
ON t.houseID = h.ID 

GROUP BY proj.id;