mysql - 合并两个表唯一列

Question

我有两个表，如下所示：

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)

我得到了使用这个的结果：“select distinct sum(money), material. created_atfrom receiptinner join materialon receipt. receipt_id= material. receipt_idgroup 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)

但我想通过忽略相同的记录来得到这个：

+------------+---------------------+
| 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)

想了很久还是没有答案，请大家帮忙，非常感谢。

标签： mysqlsql

Answer 1

只需使用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 演示