sql-server - 使用 CASE 函数自定义查询输出排序

Question

我经常发现，当我提取数据进行分析时，我会将客户下的订单数量分组到一定范围内，例如:

1-2
3-5
6-9
10-12
13-15

我使用 CASE 函数来完成此操作。但是，当您获取查询结果时，订单范围将如下列出:

1-2
10-12
13-15
3-5
6-9

当您有 1 个查询和几个订单范围组时，这很容易在 Excel 中更正。然而，当您提取许多查询时，一遍又一遍地纠正这个问题是很痛苦的。

拉动范围并正确排序的最佳方法是什么？

这是我要编写的查询示例:

SELECT 
    OrderRange = CASE
        WHEN COUNT(OrderID) BETWEEN 1 AND 5 THEN '1-5'
        WHEN COUNT(OrderID) BETWEEN 6 AND 10 THEN '6-10'
        WHEN COUNT(OrderID) > 10 THEN '10+'
        ELSE 'Error'
    END
FROM Orders
GROUP BY CASE
    WHEN COUNT(OrderID) BETWEEN 1 AND 5 THEN '1-5'
    WHEN COUNT(OrderID) BETWEEN 6 AND 10 THEN '6-10'
    WHEN COUNT(OrderID) > 10 THEN '10+'
    ELSE 'Error'
    END
ORDER BY...  ?

Answer 1

我会保留一个范围表，例如(指数未写)

CREATE TABLE Ranges (RangeSet int, MinVal int, MaxVal int, Name varchar(50));

然后例如

INSERT INTO ranges VALUES
  (1,1,5,'1-5'),(1,6,10,'6-10'),(1,11,-1,'11+'),
  (2,1,10,'1-10'),(2,11,20,'11-20'),(2,21,30,'21-30'),(2,31,-1,'31+');

你明白了。现在你做类似的事情(表和字段名称免费小说)

SELECT
  CustomerID,
  count(OrderID) AS OrderCount
FROM Orders
WHERE <whatever, e.g order_date BETWEEN ... AND ...>
GROUP BY CustomerID
HAVING OrderCount>0

正如您通常所期望的那样，但将其包装在连接到 Ranges 表的 super 查询中

SELECT
  BaseView.CustomerID as CustomerID,
  Ranges.Name as OrderRange
FROM (
  SELECT
    CustomerID,
    count(OrderID) AS OrderCount
  FROM Orders
  WHERE <whatever, e.g order_date BETWEEN ... AND ...>
  GROUP BY CustomerID
  HAVING OrderCount>0
) AS BaseView
INNER JOIN Ranges ON
  Ranges.RangeSet=<id-of-required-rangeset>
  AND BaseView.OrderCount>=Ranges.MinVal
  AND (BaseView.OrderCount<=Ranges.MaxVal OR Ranges.MaxVal=-1)
ORDER BY RangeSet.MinVal DESC
;

现在您只需提供要应用的 RangeSet，有时可能会创建一个新的 RangeSet。

免责声明:这是性能 killer