MySql：來自兩個不同表的兩個列的總和

Question

這可能是重復問題 ，但是我的問題沒有解決。

我正在嘗試使用日期確定物品的內向和外向
表。

在表1中，我們簡稱為A 我將擁有三列，即A_Dt ， A_Na ， A_Qty

在表2中，我們簡稱為“ B”。 我將擁有三列，即B_Dt ， B_N a， B_Qty

在表3中，我們將其簡稱為“ C”。 我將擁有三列，即C_Dt ， C_N a， C_Qty

表A和B向內，C向外。
我使用了修改后的查詢，但添加了第三列。

表示例：

C_Dt       C_Na  C_Qty
2016-08-01  XY  150
2016-08-03  XY  100
2016-08-04  XY  200

表B：

Date           Inward   Outward
2016-08-01      200      150
2016-08-02      100      0
2016-08-03      100      100
2016-08-04      200      200
2016-08-05      150      0

表C：

 C_Dt C_Na C_Qty 2016-08-01 XY 150 2016-08-03 XY 100 2016-08-04 XY 200 

預期產量

 Date Inward Outward 2016-08-01 200 150 2016-08-02 100 0 2016-08-03 100 100 2016-08-04 200 200 2016-08-05 150 0 

好吧，在這種情況下，我應該使用左連接，否則必須執行以下查詢。

查詢：

 select t.Dt as Date, sum(t.Qty) as Inward,sum(t.outward) as outward1 from( select A_Dt as Dt, A_Na as Na, A_Qty as Qty from a union all select B_Dt as Dt, B_Na as Na, B_Qty as Qty from b union all select C_Dt as Dt, C_Na as Na, C_Qty as outward from c )t group by t.Dt, t.Na order by t.Dt; 

跟隨錯誤：

 #1054 - Unknown column 't.outward' in 'field list' 

任何想法都會很棒。

Answer 1

首先使用union all將兩個表數據合並為一個，然后找到按日期和Na列分組的數量總和。

詢問

select t.Dt, t.Na as Inward, sum(t.Qty) as Outward from(
    select A_Dt as Dt, A_Na as Na, A_Qty as Qty from Table_A
    union all
    select B_Dt as Dt, B_Na as Na, B_Qty as Qty from Table_B
)t
group by t.Dt, t.Na
order by t.Dt;

編輯

實際上，實際上現在不需要合並TableC的數據，但是您必須使用聯接。

詢問

select t1.Dt, t1.Qty as Inward, coalesce(t2.C_Qty, 0) as Outward from(
    select t.Dt, t.Na, sum(t.Qty) as Qty from(
        select A_Dt as Dt, A_Na as Na, A_Qty as Qty from Table_A
        union all
        select B_Dt as Dt, B_Na as Na, B_Qty as Qty from Table_B
    )t
    group by t.Dt, t.Na
)t1
left join Table_C t2
on t1.Dt = t2.C_Dt
order by 1;

結果

+============+========+=========+
| Dt         | Inward | Outward |
+------------+--------+---------+
| 2016-08-01 | 200    | 150     |
| 2016-08-02 | 100    | 0       |
| 2016-08-03 | 100    | 100     |
| 2016-08-04 | 200    | 200     |
| 2016-08-05 | 150    | 0       |
+============+========+=========+

Answer 2

您的查詢只需要稍作更正

select t.Dt as Date, sum(t.Qty) as Inward, sum(t.outward) as outward1 from(
   select A_Dt as Dt, A_Na as Na, A_Qty as Qty, 0 as outward from a
   union all
   select B_Dt as Dt, B_Na as Na, B_Qty as Qty, 0 as outward from b
   union all
   select C_Dt as Dt, C_Na as Na, 0 as Qty, C_Qty as outward from c
)t
-- where Na = 'XY'
group by t.Dt, t.Na
order by t.Dt;