Combine two tables unique column

Question

I have two tables like shown as below:

mysql> select*from receipt;                                                                                
+----+------------+-------+---------------------+
| id | receipt_id | money | created_at          |
+----+------------+-------+---------------------+
|  1 | receipt_3  |   100 | 2018-10-30 00:00:00 |
|  2 | receipt_4  |   200 | 2018-10-29 00:00:00 |
|  3 | receipt_5  |   300 | 2018-10-31 00:00:00 |
+----+------------+-------+---------------------+
3 rows in set (0.00 sec)

mysql> select*from material;
+----+------------+---------------------+
| id | receipt_id | created_at          |
+----+------------+---------------------+
|  1 | receipt_3  | 2018-10-30 00:00:00 |
|  2 | receipt_3  | 2018-10-30 00:00:00 |
|  3 | receipt_5  | 2018-10-31 00:00:00 |
+----+------------+---------------------+
3 rows in set (0.00 sec)

I have got the result use this: "select distinct sum(money),material.created_at from receipt inner join material on receipt.receipt_id=material.receipt_id group by material.created_at;"

+------------+---------------------+
| sum(money) | created_at          |
+------------+---------------------+
|        200 | 2018-10-30 00:00:00 |
|        300 | 2018-10-31 00:00:00 |
+------------+---------------------+
2 rows in set (0.00 sec)

but I want to get this with ignoring same record:

+------------+---------------------+
| sum(money) | created_at          |
+------------+---------------------+
|        100 | 2018-10-30 00:00:00 |
|        300 | 2018-10-31 00:00:00 |
+------------+---------------------+
2 rows in set (0.00 sec)

Have thought for a long time but no answer,please help ,thanks a lot.

Answer 1

Just use sum(distinct money) :

select sum(distinct money) as sum_money,
       m.created_at 
  from receipt r join material m 
    on r.receipt_id=m.receipt_id 
 group by m.created_at;

+------------+---------------------+
| sum_money  | created_at          |
+------------+---------------------+
|        100 | 2018-10-30 00:00:00 |
|        300 | 2018-10-31 00:00:00 |
+------------+---------------------+

DB-Fiddle Demo