Mysql 联合查询返回意外结果

我组合了两个查询以获得所需的结果，但它没有给出我想要的结果

查询是这样的

SELECT COALESCE(SUM(rd.AMOUNT),0) as total from revenue_d AS rd JOIN  revenue_m AS rem on rd.RV_ID = rem.RV_ID Where MONTH(rd.SCROLL_DATE) = 5   and YEAR(rd.SCROLL_DATE)= 2016

Union 

SELECT COALESCE(SUM(rd.AMOUNT),0) as total from revenue_d AS rd JOIN revenue_m AS rem on rd.RV_ID = rem.RV_ID Where MONTH(rd.SCROLL_DATE) = 6 and YEAR(rd.SCROLL_DATE)= 2016;

它给我的结果是这样的

 +---------------+
 |     total     |
 +---------------+
 |       0       |
 +---------------+

 +---------------+
 |     total     |
 +---------------+
 |       0       |
 +---------------+
 |       0       |
 +---------------+

当我想要这样的时候

 +---------------+
 |     total     |
 +---------------+
 |       0       |
 +---------------+

 +---------------+
 |     total     |
 +---------------+
 |       0       |
 +---------------+
 |       0       |
 +---------------+

---

甚至使用了Union，但仍然得到相同的结果。

我认为总是执行最后一个查询，所以您应该这样写

(first Query) UNION ALL (second query);

请尝试此查询

(SELECT COALESCE(SUM(rd.AMOUNT),0) AS total 
    FROM revenue_d AS rd 
    JOIN  revenue_m AS rem ON rd.RV_ID = rem.RV_ID 
    WHERE MONTH(rd.SCROLL_DATE) = 5  AND YEAR(rd.SCROLL_DATE)= 2016)

  UNION ALL

(SELECT COALESCE(SUM(rd.AMOUNT),0) AS total 
    FROM revenue_d AS rd 
    JOIN revenue_m AS rem ON rd.RV_ID = rem.RV_ID 
    WHERE MONTH(rd.SCROLL_DATE) = 6 AND YEAR(rd.SCROLL_DATE)= 2016);

---

您需要

union all

<代码>联合删除重复项，因此：

SELECT COALESCE(SUM(rd.AMOUNT),0) as total
from revenue_d rd JOIN
     revenue_m rem
     on rd.RV_ID = rem.RV_ID
Where MONTH(rd.SCROLL_DATE) = 5   and YEAR(rd.SCROLL_DATE)= 2016

Union all

SELECT COALESCE(SUM(rd.AMOUNT),0) as total
from revenue_d rd JOIN
     revenue_m rem
     on rd.RV_ID = rem.RV_ID
Where MONTH(rd.SCROLL_DATE) = 6 and YEAR(rd.SCROLL_DATE)= 2016;

但是，更自然的做法是使用

group by

编写此查询，尽管不带值的句点将丢失：

SELECT YEAR(rd.SCROLL_DATE) as yyyy,
       MONTH(rd.SCROLL_DATE) as mm,
       COALESCE(SUM(rd.AMOUNT), 0) as total
from revenue_d rd JOIN
     revenue_m rem
     on rd.RV_ID = rem.RV_ID
Where MONTH(rd.SCROLL_DATE) IN (5, 6) and YEAR(rd.SCROLL_DATE)= 2016;

或者，使用条件聚合（将值放在两列中：

SELECT YEAR(rd.SCROLL_DATE) as yyyy,
       SUM(CASE WHEN MONTH(rd.SCROLL_DATE) = 5 then rd.AMOUNT else 0) as total_05,
       SUM(CASE WHEN MONTH(rd.SCROLL_DATE) = 6 then rd.AMOUNT else 0) as total_06
from revenue_d rd JOIN
     revenue_m rem
     on rd.RV_ID = rem.RV_ID
Where MONTH(rd.SCROLL_DATE) IN (5, 6) and YEAR(rd.SCROLL_DATE) = 2016;

工会和全体工会的区别是什么

联合删除重复的行

---

UNION ALL不会删除重复的行。

改用

UNION ALL

。我这样做的同时仍然得到相同的结果

UNION ALL

应该可以完成这项工作。我认为其中一个查询返回

null

。您可以尝试类似于

coalesce（QUERY1，0）的方法

也许你在一个月内没有任何记录。请检查每个月的记录数谢谢。我使用的phpmyadmin在解析'all'关键字时有一个错误。因此，即使使用union all，我也只得到一个结果。现在我安装了msql workbench，我得到了我想要的结果。