Question

我正在使用Northwind数据集中的表格（可以从下面的查询生成）

+-----------+-----------+
| NumOrders | CustCount |
+-----------+-----------+
|         1 |         1 |
|         2 |         2 |
|         3 |         7 |
|         4 |         6 |
|         5 |        10 |
|         6 |         8 |
|         7 |         7 |
|         8 |         4 |
|         9 |         5 |
|        10 |        11 |
|        11 |         4 |
|        12 |         3 |
|        13 |         3 |
|        14 |         6 |
|        15 |         3 |
|        17 |         1 |
|        18 |         3 |
|        19 |         2 |
|        28 |         1 |
|        30 |         1 |
|        31 |         1 |
+-----------+-----------+`

而且我想编写一个查询，以提供x个制作y个订单的人数的直方图

select 
    case 
        when NumOrders > 0 and NumOrders <= 5 then '0 - 5'
        when NumOrders > 5 and NumOrders <=10 then '6 - 10'
        else '10+' 
    end as Bucket,
    CustomerCount = sum(CustCount)
from (
    select 
        NumOrders,
        CustCount = count(*) 
    from (
        select * 
        from (
            select 
                CustomerID, 
                count(*) as NumOrders
            from orders 
            group by CustomerID
            ) c
        ) b
    group by NumOrders
    )a
group by 
(
    case 
        when NumOrders > 0 and NumOrders <= 5 then '0 - 5'
        when NumOrders > 5 and NumOrders <=10 then '6 - 10'
        else '10+' 
    end 
)

从上面的查询中，我得到此输出，该输出的顺序不正确。

+--------+---------------+
| Bucket | CustomerCount |
+--------+---------------+
| 0 - 5  |            26 |
| 10+    |            28 |
| 6 - 10 |            35 |
+--------+---------------+

我希望将其订购为

+--------+---------------+
| Bucket | CustomerCount |
+--------+---------------+
| 0 - 5  |            26 |
| 6 - 10 |            35 |
| 10+    |            28 |
+--------+---------------+

有人可以建议如何正确订购吗？

Answer 1

您只需要

Order by NumOrders

在查询的最后

Answer 2

我看不到问题的哪一部分无法解决...

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(NumOrders SERIAL PRIMARY KEY
,CustCount INT NOT NULL
);

INSERT INTO my_table VALUES
(1 ,1),
(2 ,2),
(3 ,7),
(4 ,6),
(5 ,0),
(6 ,8),
(7 ,7),
(8 ,4),
(9 ,5),
(10,1),
(11,4),
(12,3),
(13,3),
(14,6),
(15,3),
(17,1),
(18,3),
(19,2),
(28,1),
(30,1),
(31,1);

SELECT CASE WHEN numorders BETWEEN 0 AND  5 THEN '0-5'
            WHEN numorders BETWEEN 6 AND 10 THEN '6-10'
            ELSE '+10' END bucket
      , COUNT(*) total
   FROM my_table
  GROUP
     BY bucket
  ORDER
     BY numorders;
+--------+-------+
| bucket | total |
+--------+-------+
| 0-5    |     5 |
| 6-10   |     5 |
| +10    |    11 |
+--------+-------+

无法订购mysql中的列

2 个答案: