如何连接同一个表中的两列答案

【问题标题】：How to Join two columns in same table如何连接同一个表中的两列
【发布时间】：2020-05-13 13:42:29
【问题描述】：

SELECT CAST(`last_charged_date`  AS DATE) AS Date_time, COUNT(*) AS

Charged_Count, SUM(last_charge_amt) AS 收入来自subscriber 按演员分组（last_charged_date 日期）

SELECT CAST(created_date AS DATE) AS Date_time, COUNT(*) AS Registered_Count 来自subscriber 按演员分组（created_date 日期）

我想将last_charged_date 和created_date 合并为一列，并且需要根据日期将 Charged_Count、Revenue 和 Registered_Count 显示为单独的列

【问题讨论】：

你考虑过union 吗？
Join 是一个非常宽松的术语 - 如果您能显示您的预期输出，它会有所帮助。
@ScaryWombat for union 两个查询应该具有相同数量的相同数据类型的列。
分享您的示例输出
@KarthikeyanVaithilingam 当然，你是对的。不过，添加一个虚拟列将是微不足道的。现在更容易看到它已经整理了一点。

标签： java mysql sql database

【解决方案1】：

你可以使用union all：

select date, 
       sum ( col = 'last_charged' ) as Charged_Count,
       sum (case when col = 'last_charged' then Revenue else 0 end ) as Revenue,
       sum ( col = 'created_date' ) as Registered_Count
from (select CAST(s.`last_charged_date`  AS DATE) as date, 
             s.`last_charge_amt` as Revenue, 'last_charged' as col 
      from `subscriber` s union all
      select CAST(s1.`created_date`  AS DATE) as created_date, 
             0, 'created_date' as col 
      from `subscriber` s1
    ) t
group by date;

【讨论】：

【解决方案2】：

使用子查询和连接，但在这种情况下，在任何日期中，子查询的数据都会更少

select a.*,b.* from ( SELECT CAST(`last_charged_date`  AS DATE) AS Date_time, COUNT(*) AS 
 Charged_Count, SUM(`last_charge_amt`) AS Revenue 
    FROM `subscriber` 
    GROUP BY CAST(`last_charged_date`  AS DATE)
) a join 
(
 SELECT CAST(`created_date` AS DATE) AS Date_time, COUNT(*) AS Registered_Count 
    FROM `subscriber` 
    GROUP BY CAST(`created_date` AS DATE)
) b on a.Date_time=b.Date_time

【讨论】：

【解决方案3】：

试试这个查询，

SELECT CAST(`last_charged_date`  AS DATE) AS Date_time, COUNT(*) AS  Charged_Count, SUM(last_charge_amt) AS Revenue, ksolangi.Date_time, Date_time.Registered_Count
FROM subscriber 
LEFT OUTER JOIN ( SELECT CAST(created_date AS DATE) AS Date_time, COUNT(*) AS Registered_Count FROM subscriber GROUP BY CAST(created_date AS DATE) ) AS ksolangi ON ksolangi.Date_time = CAST(last_charged_date AS DATE)
GROUP BY CAST(last_charged_date AS DATE)

【讨论】：

这个查询对我不起作用。 Registered_Count 在分配为 Registered_Count 之前不能使用