Sql postgres查询销售预测

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这是我的疑问： ==========================================

我希望得到这样的结果： ============

要求：

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目前我们有销售数据。需要了解销售预测，好像销售额将增加10%、20%、30%等。例如：今天，产品的销售额范围（0-99）为300。如果销售额增加10%，销售额增加10%应该是330

我是遗漏了什么，还是您只需要使用：

  SELECT SUM(sub_total) AS sales,
         CASE WHEN (sub_total<100) THEN '0-99' 
              WHEN (sub_total>=100 AND sub_total<200) THEN '100-199' 
              WHEN (sub_total>=200 AND sub_total<300) THEN '200-299' 
              WHEN (sub_total>=300 AND sub_total<400) THEN '300-399' 
              WHEN (sub_total>=400 AND sub_total<500) THEN '400-499' 
              ELSE '500+'
         END AS product_sales_range,
         SUM(sub_total) * 1.1 AS sales_increase_by_10Percent,
         SUM(sub_total) * 1.2 AS sales_increase_by_20Percent
    FROM order_item 
GROUP BY sub_total

选择总和（小计）作为销售额，
当（sub_total=100，sub_total=200，sub_total=300，sub_total=400，sub_total=400，sub_total=200，sub_total=200，sub_total=300，sub_total=400，sub_total=400，sub_total=200）的情况
sales       product_sales_range
-----       -------------------

10398.96        200-299
600         100-199
300         0-99
7699.78     300-399
6799.32     100-199
600         0-99
26599.24        500+

sales       product_sales_range sales_increase_by_10%   sales_increase_by_20%
-----       ------------------- ------------------  ------------------

10398.96        200-299
600         100-199
300         0-99
7699.78     300-399
6799.32     100-199
600         0-99
26599.24        500+

  SELECT SUM(sub_total) AS sales,
         CASE WHEN (sub_total<100) THEN '0-99' 
              WHEN (sub_total>=100 AND sub_total<200) THEN '100-199' 
              WHEN (sub_total>=200 AND sub_total<300) THEN '200-299' 
              WHEN (sub_total>=300 AND sub_total<400) THEN '300-399' 
              WHEN (sub_total>=400 AND sub_total<500) THEN '400-499' 
              ELSE '500+'
         END AS product_sales_range,
         SUM(sub_total) * 1.1 AS sales_increase_by_10Percent,
         SUM(sub_total) * 1.2 AS sales_increase_by_20Percent
    FROM order_item 
GROUP BY sub_total