如何在查询中添加辅助列？

Question

我的 table 可能是这样的：

|     Email         |     ID    |  Order_date  |    Total     |
| ----------------- | --------- | ------------ | ------------ |
|customerA@gmail.com|     1     | 01-01-2019   |     500      |
|customerB@gmail.com|     2     | 02-01-2019   |    1000      |
|customerC@gmail.com|     3     | 03-01-2019   |    1000      |
|customerD@gmail.com|     4     | 04-01-2019   |    2000      |
|customerA@gmail.com|     5     | 05-01-2019   |    3000      |
|customerB@gmail.com|     6     | 06-01-2019   |    500       |
|customerC@gmail.com|     7     | 03-01-2019   |    1000      |
|customerA@gmail.com|     8     | 05-01-2019   |    3000      |
|customerB@gmail.com|     9     | 09-01-2019   |    2000      |
|customerA@gmail.com|    10     | 10-01-2019   |    4000      |
|customerB@gmail.com|    11     | 02-01-2019   |    1000      |
|customerA@gmail.com|    12     | 12-01-2019   |    2000      |

我想添加一个包含订单数量的辅助列，但不进行任何额外的分组。我的梦想 table 是这样的：

|     Email         |     ID    |  Order_date  |   Total      | Number of orders |
| ----------------- | --------- | ------------ | ------------ | ---------------- |
|customerA@gmail.com|     1     | 01-01-2019   |     500      |      5           |
|customerB@gmail.com|     2     | 02-01-2019   |    1000      |      4           |
|customerC@gmail.com|     3     | 03-01-2019   |    1000      |      2           |
|customerD@gmail.com|     4     | 04-01-2019   |    2000      |      1           |
|customerA@gmail.com|     5     | 05-01-2019   |    3000      |      5           |
|customerB@gmail.com|     6     | 06-01-2019   |    500       |      4           |
|customerC@gmail.com|     7     | 03-01-2019   |    1000      |      2           |
|customerA@gmail.com|     8     | 05-01-2019   |    3000      |      5           |
|customerB@gmail.com|     9     | 09-01-2019   |    2000      |      4           |
|customerA@gmail.com|    10     | 10-01-2019   |    4000      |      5           |
|customerB@gmail.com|    11     | 02-01-2019   |    1000      |      4           |
|customerA@gmail.com|    12     | 12-01-2019   |    2000      |      5           |

正如您可能猜到的那样，我想根据购物订单的数量执行进一步的计算（如总和或平均值）。我的 SQL 查询可能如下所示：

SELECT AVG(Total)
FROM
(SELECT ...
...
...
WHERE ...
...
...
GROUP BY ...
HAVING COUNT(Number_of_orders > 1) AND COUNT(Number_of_orders < 5) x

或者类似的东西。只是为了让您了解为什么我认为我需要辅助列。

我原以为这很容易，但我已经花了很多时间在这上面，所以任何类型的建议或帮助都将不胜感激！

Answer 1

假设 'Email' 是您要按订单数分组的列，这应该会得到您想要的 table。

SELECT T.Email, T.ID, T.Date, T.Total, TT.Count
FROM Table T
INNER JOIN (
   SELECT Email, Count(Email) as Count
   FROM Table
   GROUP BY Email) TT 
ON T.Email = TT.Email

Answer 2

如果你的数据库引擎支持partitioning:

select * , count(*) over (partition by Email) as OrderCount
from tablename

如何在查询中添加辅助列？

How to add auxiliary column inside query?

sql

soql