Question

我有一个查询，该查询返回按月分组的销售总额。我想添加一列，该列返回与上一行相比百分比的增长/减少。

我已经尝试使用CREATE TEMPORARY TABLE，创建变量@var :=，但实际上没有任何作用。理想情况下，我的结果将是：

Month | Sales | Perc
1     | 100   | 0
2     | 150   | 50
3     | 100   | -33.33

要进行的计算是：((actual_value - previous_value) / previous_value) *100

关于表格，我使用sales，products，sales_items，因此我检索按月分组的销售总额的查询是：

SELECT 
    MONTH(s.sale_date) AS Month,
    SUM(p.retail_price * si.quantity) AS Sales_Amount
FROM sales s
INNER JOIN sales_items si ON s.sale_id = si.sale_id
INNER JOIN products p ON si.product_id = p.product_id
WHERE YEAR(s.sale_date) = '2018'
GROUP BY month 
ORDER BY month;

由于我使用SUM来汇总销售项目并将其汇总到每个sale_id中，并且按月分组后，使用该值到新列中似乎很复杂，因此如果有人对如何做有想法，那就太好了。

Answer 1

在MySQL 8.0中，您可以将聚合查询转换为子查询，并使用窗口函数LAG访问上个月的值，例如：

SELECT 
    Sales_Month, 
    Sales_Amount, 
    ( Sales_Amount - LAG(Sales_Amount) OVER(ORDER BY Sales_Month) )
        /LAG(Sales_Amount) OVER(ORDER BY Sales_Month) * 100 AS Percent_Increase
FROM (
    SELECT 
        MONTH(s.sale_date) AS Sales_Month,
        SUM(p.retail_price * si.quantity) AS Sales_Amount
    FROM sales s
    INNER JOIN sales_items si ON s.sale_id = si.sale_id
    INNER JOIN products p ON si.product_id = p.product_id
    WHERE YEAR(s.sale_date) = '2018'
    GROUP BY Sales_Month 
) x
ORDER BY Sales_Month

Answer 2

您可以添加新列“ PrevMonthSales”。为此，您必须将查询与自身结合起来：

SELECT ...
FROM
(...your_query...) s1
LEFT JOIN (...your_query...) s2 ON s2.Month = s1.Month - 1

在您的情况下：

SELECT s1.Month, s1.Sales_Amount, 
    COALESCE(s2.Sales_Amount, 0) "PrevMonthSales",
CASE
    WHEN s1.Sales_Amount = 0 THEN 0
    ELSE     (s1.Sales_Amount - COALESCE(s2.Sales_Amount, 0)) / s1.Sales_Amount 
END "Percent"
FROM
    (...your_query...) s1
    LEFT JOIN (...your_query...) s2 ON s2.Month = s1.Month - 1

Answer 3

置于名为month_sales的临时表下面

SELECT 
MONTH(s.sale_date) AS Month,
SUM(p.retail_price * si.quantity) AS Sales_Amount
FROM sales s
INNER JOIN sales_items si ON s.sale_id = si.sale_id
INNER JOIN products p ON si.product_id = p.product_id
WHERE YEAR(s.sale_date) = '2018'
GROUP BY month 
ORDER BY month;

查询以查找月与月之间的差异是：

SELECT *, 
case 
when m2.Sales_Amount is null then 0 
else (m2.Sales_Amount - m1.Sales_Amount)/m1.Sales_Amount 
end as Perc
FROM month_sales m1
left Join month_sales m2
WHERE m1.month = m2.month - 1

如何使用以前的值计算增加/减少的百分比

3 个答案: