sum（）列用于具有相同id的多个查询并显示到联接表

Question

我可以选择一列的总和并将其显示在与其连接的另一个表中吗？

tblmedstockin
+--------------+-------+-----------------+-------------+----------------+
| medstockinid | medid | stockinquantity | stockindate | stockinexpdate |
+--------------+-------+-----------------+-------------+----------------+
|            1 |  1001 |             100 | 2019-01-29  | 2019-12-16     |
|            2 |  1001 |             100 | 2019-01-29  | 2019-12-16     |
|            3 |  1001 |              12 | 2019-01-29  | 2019-01-29     |
|            5 |  1004 |               4 | 2019-01-29  | 2019-01-29     |
|            6 |  1004 |              20 | 2019-01-30  | 2019-01-30     |

预期结果：

tblmedstock
+------------+-------+----------+-----------+-----------------+--------------+
| medstockid | medid | category | medname   | stockinquantity | stockcritqty |
+------------+-------+----------+-----------+-----------------+--------------+
|       1001 |  1001 | Tablet   | Losartan  |             212 |          100 |
|       1004 |  1004 | Tablet   | Metformin |              24 |          100 |
+------------+-------+----------+-----------+-----------------+--------------+

我想从tblmedstockin中求和（库存数量）并显示为tblmedstock上的一列。

尝试了以下代码，但必须手动更改每个查询的ID：

select a.medstockid, c.medid, c.category, c.medname, (select sum(stockinquantity)from tblmedstockin where medid = 1001) as stockinquantity, a.stockcritqty from tblmedstock a inner join tblmedstockin b on a.medstockinid = b.medstockinid inner join tblmedicine c on a.medid = c.medid where a.medid = 1001

-> union

-> select a.medstockid, c.medid, c.category, c.medname, (select sum(stockinquantity)from tblmedstockin where medid = 1004) as stockinquantity, a.stockcritqty from tblmedstock a inner join tblmedstockin b on a.medstockinid = b.medstockinid inner join tblmedicine c on a.medid = c.medid where a.medid = 1004;

无需手动设置ID就能自动完成吗？

Answer 1

您只需要按原样联接表并在此处使用GROUP BY（在此处对表关系进行一些假设）：

select a.medstockid, c.medid, c.category, c.medname, sum(b.stockinquantity), a.stockcritqty 
from tblmedstock a 
   Removed since this doesn't appear to be used in this query*/
   inner join tblmedstockin b on a.medstockinid = b.medstockinid*/
   inner join tblmedicine c on a.medid = c.medid 
WHERE a.medid in (1001,1004)
GROUP BY a.medstockid, c.medid, c.category, c.medname, a.stockcritqty