mysql从不同的表中选择总和2行

Question

我一直在尝试找到对 2 个不同表中的 2 行求和的正确方法。

我可以使用这两个查询轻松识别要求和的行:

select * 
from   vui_trading_review_form_client 
where  month = '201202' and client_id='TOTALS';

+--------+------------+-----------+-----------------+-----------------+-----------------+----------------+----------+
| month  | dt_end     | client_id | amt_balance_GBP | amt_balance_EUR | amt_balance_USD | dt_working_day | order_no |
+--------+------------+-----------+-----------------+-----------------+-----------------+----------------+----------+
| 201202 | 2012-02-29 | TOTALS    |            2    |             3   |               4 | 2012-02-29     |        2 |
+--------+------------+-----------+-----------------+-----------------+-----------------+----------------+----------+


select * 
from   vui_trading_review_form_bank 
where  month = '201202' and provider='TOTALS';

+--------+------------+----------+-----------------+-----------------+-----------------+----------+
| month  | dt_end     | provider | amt_balance_GBP | amt_balance_EUR | amt_balance_USD | order_no |
+--------+------------+----------+-----------------+-----------------+-----------------+----------+
| 201202 | 2012-02-29 | TOTALS   |              1  |               1  |              1 |        3 |
+--------+------------+----------+-----------------+-----------------+-----------------+----------+

我想要实现的是一个如下所示的表格

+-----------------+-----------------+-----------------+
| amt_balance_GBP | amt_balance_EUR | amt_balance_USD |
+-----------------+-----------------+-----------------+
| 1               |          2      |             3   |
+-----------------+-----------------+-----------------+

前 3 个总计减去后 3 个总计。

我尝试过加入，但我真的很难获得正确的结果。

如有任何建议，我们将不胜感激。

Answer 1

试试这个:

SELECT  (a.amt_balance_GBP - b.amt_balance_GBP) Total_GBP,
        (a.amt_balance_EUR - b.amt_balance_EUR) Total_EUR,
        (a.amt_balance_USD - b.amt_balance_USD) Total_USD
FROM vui_trading_review_form_client a INNER JOIN vui_trading_review_form_bank b
        on (a.Client_ID = b. provider) AND
           (a.Month = b.Month)
WHERE a.month = '201202' and b.provider='TOTALS';

或者如果它不符合您的需求，请尝试使用LEFT JOIN

SELECT  (a.amt_balance_GBP - COALESCE(b.amt_balance_GBP,0)) Total_GBP,
        (a.amt_balance_EUR - COALESCE(b.amt_balance_EUR,0)) Total_EUR,
        (a.amt_balance_USD - COALESCE(b.amt_balance_USD,0)) Total_USD
FROM vui_trading_review_form_client a LEFT JOIN vui_trading_review_form_bank b
        on (a.Client_ID = b. provider) AND
           (a.Month = b.Month)
WHERE a.month = '201202' and b.provider='TOTALS';