Question

我有两个数据库，有两个相似的表：

数据库1

id         date              value   
---       -----------        --------- 
1          2016-04-20        900  
2          2016-05-02        455
3          2016-05-03        90
4          2016-05-02        855

数据库2

SELECT date, SUM(value) As TOTAL FROM tablename   
WHERE date >= DATE_SUB( NOW( ) , INTERVAL 1 YEAR )   
GROUP BY date ORDER BY date

我对每个数据库都有这个查询：

        Database1                              Database2
 date          TOTAL                      date          TOTAL  
------       ---------                   -------        -------  
2016-05-01     234                       2016-04-20       900  
2016-05-02     567                       2016-05-02       1310  
2016-05-03     1100                      2016-05-03       90

返回以下结果：

        Cobined Results 
 date          TOTAL_DB1      TOTAL_DB2  
------       ---------        ----------   
2016-04-20       0               900     
2016-05-01     234                 0         
2016-05-02     567              1310  
2016-05-03    1100                90

现在我想要一个根据日期结合这两个结果的查询，我的预期输出是：

ActivityManager

Answer 1

使用union all，然后按组date进行聚合：

SELECT `date`, sum(TOTAL_DB1) as TOTAL_DB1, sum(TOTAL_DB2) as TOTAL_DB2 
FROM (
    SELECT date, SUM(value) As TOTAL_DB1, 0 AS TOTAL_DB2 FROM Database1   
    WHERE date >= DATE_SUB( NOW( ) , INTERVAL 1 YEAR )   
    GROUP BY date
    UNION ALL
    SELECT date, 0 AS TOTAL_DB1, SUM(value) As TOTAL_DB2 FROM Database2  
    WHERE date >= DATE_SUB( NOW( ) , INTERVAL 1 YEAR )   
    GROUP BY date
) t
GROUP BY `date`
ORDER BY `date`

Check Demo Here

联合结果两个数据库查询

1 个答案: