使用Group By从两个表中减去两列

Question

我有4张桌子。

CREATE TABLE Branch(
  ID INT,
  Name VARCHAR(50)
);

INSERT INTO Branch VALUES 
(1,'A'), (2,'B');

CREATE TABLE Product(
  ID INT,
  Name VARCHAR(50)
);

INSERT INTO Product VALUES 
(1,'X'), (2,'Y');

CREATE TABLE StockIn(
  ID INT,
  ProductId INT,
  Quantity INT,
  BranchId INT
);

INSERT INTO StockIn VALUES 
(1,1,10,1),
(2,1,20,1),
(3,1,50,2),
(4,1,10,2);

CREATE TABLE StockOut(
  ID INT,
  ProductId INT,
  Quantity INT,
  BranchId INT
);

INSERT INTO StockOut VALUES 
(1,1,5,1),
(2,1,21,1),
(3,1,45,2),
(4,1,5,2);

现在我想从这些（StockIn-StockOut）计算股票。

通过使用下面的查询我通过分组他们的分支从库存表获得stockin和stockout。

StockIn

select BranchId, ifnull(sum(Quantity),0) Quantity from stockin where productid=1 group by BranchId;

脱销

select BranchId, ifnull(sum(Quantity),0) Quantity from stockout where productid=1 group by BranchId;

我想像这样显示结果

Answer 1

• 对于每个单独的Select查询结果，获取一个附加字段，即factor 。 其库存值为+1 ，库存为-1 。
• 使用Union All组合各个选择查询的结果，并将结果集用作派生表 。
• 现在，在BranchId的分组上再简单地再次使用因子。

请尝试以下查询：

SELECT derived_t.BranchId, 
       SUM(derived_t.factor * derived_t.quantity) AS Quantity 
FROM 
(
 select BranchId, 
        ifnull(sum(Quantity),0) as quantity, 
        1 as factor 
 from stockin 
 where productid=1 
 group by BranchId

 UNION ALL 

 select BranchId, 
        ifnull(sum(Quantity),0) Quantity, 
        -1 as factor
 from stockout 
 where productid=1 
 group by BranchId
) AS derived_t 

GROUP BY derived_t.BranchId

Answer 2

使用stockin和stockout之间的左连接，这里你需要左连接，因为你可能有stockin但可能没有

离开加入你的2个quires

select t1.branchId, t1.quantity - coalesce(t2.quantity,0) result
from (
    select BranchId, coalesce(sum(Quantity),0) Quantity 
    from stockin 
    where productid=1 
    group by BranchId
) t1 left join (
   Select BranchId, coalesce(sum(Quantity),0) Quantity 
   from stockout
   where productid=1 
   group by BranchId
) t2 on t1.BranchId = t2.BranchId

branchId    result
1            4
2           10

http://sqlfiddle.com/#!9/c549d3/6

Answer 3

您可以在两个查询之间使用连接

select a.branchId, a.quantity - ifnull(b.quantity,0) result
from (
    select BranchId, ifnull(sum(Quantity),0) Quantity 
    from stockin 
    where productid=1 
    group by BranchId
) a left join (
   Select BranchId, ifnull(sum(Quantity),0) Quantity 
   from stockout
   where productid=1 
   group by BranchId
) b on a.BranchId = b.BranchId

Answer 4

select branchid, sum(quantity) total
from
(
select branchid,quantity from stockin
union all
select branchid, quantity*-1 from stockout
) x
group by branchid;

http://sqlfiddle.com/#!9/c549d3/1