SQL查询：未获得正确的输出

我有下表，而不是零在添加天和删除天我想要尊重的输出 有人能帮我得到正确的SQL语句吗

我试了很多

E_ID H_ID   ADD_DAYS  REMOVE_DAYS
1   1   "2" "0"
2   2   "4" "0"
2   2   "0" "1"
3   3   "2" "0"
3   3   "0" "4"
3   4   "0" "4"

实际的

E_ID H_ID   ADD_DAYS  REMOVE_DAYS
1   1   "2" "0"
2   2   "4" "0"
2   2   "0" "1"
3   3   "2" "0"
3   3   "0" "4"
3   4   "0" "4"

期望

E_ID H_ID   ADD_DAYS  REMOVE_DAYS
1   1   "2" "0"
2   2   "4" "1"
3   3   "2" "4"
3   4   "0" "4"

你可以在下面试试-

select e_id, h_id, max(ADD_DAYS),max(REMOVE_DAYS)
from tablename
group by e_id, h_id

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你到底试过什么？您使用的是哪种DBMS产品？