计算红移中每个产品的余额答案

【问题标题】：Calculate balance amount per prodcuct in redshift计算红移中每个产品的余额
【发布时间】：2023-01-18 15:56:41
【问题描述】：

CREATE TABLE inventory (
    id SERIAL PRIMARY KEY,
    stock_date DATE,
    product VARCHAR(255),
    inbound_quantity INT,
    outbound_quantity INT
);

INSERT INTO inventory
(stock_date, product, inbound_quantity, outbound_quantity
)
VALUES 
('2020-01-01', 'Product_A', '900', '0'),
('2020-01-02', 'Product_A', '0', '300'),
('2020-01-03', 'Product_A', '400', '250'),
('2020-01-04', 'Product_A', '0', '100'),
('2020-01-05', 'Product_A', '700', '500'),
  
('2020-01-03', 'Product_B', '850', '0'),
('2020-01-08', 'Product_B', '100', '120'),
('2020-02-20', 'Product_B', '0', '360'),
('2020-02-25', 'Product_B', '410', '230'),

预期结果：

stock_date	product	inbound_quantity	outbound_quantity	balance
2020-01-01	Product_A	900	0	900
2020-01-02	Product_A	0	300	600
2020-01-03	Product_A	400	250	750
2020-01-04	Product_A	0	100	650
2020-01-05	Product_A	700	500	850
2020-01-03	Product_B	740	0	740
2020-01-08	Product_B	100	120	720
2020-02-20	Product_B	0	360	360
2020-02-25	Product_B	410	230	540
2020-03-09	Product_B	290	0	830

我想计算每个产品的余额。
到目前为止，我已经能够在下面开发这个查询，但它不起作用。
我收到错误 window "product" does not exist。

SELECT 
iv.stock_date AS stock_date,
iv.product AS product,
iv.inbound_quantity AS inbound_quantity,
iv.outbound_quantity AS outbound_quantity,
SUM(iv.inbound_quantity - iv.outbound_quantity) OVER 
(product ORDER BY stock_date ASC ROWS UNBOUNDED PRECEDING) AS Balance
FROM inventory iv
GROUP BY 1,2,3,4
ORDER BY 2,1;

我需要如何修改查询才能使其工作？

【问题讨论】：

标签： sql postgresql

【解决方案1】：

错误消息“product”不存在是因为您试图在 OVER 子句中引用列“product”，但它不包含在 GROUP BY 子句中。

要解决此问题，您需要在 GROUP BY 子句中包含“product”列，并在 OVER 子句中添加一个 partition by 子句，以便 SUM 函数计算每个产品的余额。

试试这个查询：

SELECT 
    iv.stock_date AS stock_date,
    iv.product AS product,
    iv.inbound_quantity AS inbound_quantity,
    iv.outbound_quantity AS outbound_quantity,
    SUM(iv.inbound_quantity - iv.outbound_quantity) OVER 
    (PARTITION BY product ORDER BY stock_date ASC ROWS UNBOUNDED PRECEDING) AS Balance
FROM inventory iv
GROUP BY 1,2,3,4
ORDER BY 2,1;

这样，SUM 函数只会对每个产品的 inbound_quantity - outbound_quantity 求和，而不是对所有产品求和。

查询将返回预期的结果。

【讨论】：

【解决方案2】：

你快到了

您应该在产品前面添加分区

SELECT 
iv.stock_date AS stock_date,
iv.product AS product,
iv.inbound_quantity AS inbound_quantity,
iv.outbound_quantity AS outbound_quantity,
SUM(iv.inbound_quantity - iv.outbound_quantity) OVER 
(partition by product ORDER BY stock_date ASC ROWS UNBOUNDED PRECEDING) AS Balance
FROM inventory iv
GROUP BY 1,2,3,4
ORDER BY 2,1;

所以，它应该是这样的

【讨论】：