mysql - Subtract two columns from two tables with Group By

Question

I have 4 tables.

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);

Now i want to calculate stock from these (StockIn-StockOut).

by using below query i got stockin and stockout from stock tables by grouping thier branches.

StockIn

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

StockOut

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

and i want to show the result like this

标签： mysqlsqldatabase

Answer 1

• 对于每个单独的 Select 查询结果，获取一个附加字段，即factor。进货时其值为+1，缺货时为-1。
• 使用Union All组合单个选择查询的结果，并将结果集用作派生表。
• 现在，只需在 BranchId 的分组上再次进行求和，乘以因子。

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