如何将两个MySQL结果合并为一个？

我有两个结果：

- | month      | first_time_buyers |
- | 2016-07-01 |                 2 |
- | 2016-08-01 |                 2 |

- | month      | returned_buyers |
- | 2016-08-01 |               1 |
- | 2016-09-01 |               2 |

我想将它们合并为一个结果，如：

 - | date       | first_time_buyers | returned_buyers |
 - | 2016-07-01 |                 2 |               0 |
 - | 2016-08-01 |                 2 |               1 |
 - | 2016-09-01 |                 0 |               2 |

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由于MySQL中没有完全联接，因此需要在外部查询中使用group by来联合所有两个联接查询

SELECT month, 
       first_time_buyers, 
       returned_buyers 
FROM   (SELECT table1.month, 
               Ifnull(first_time_buyers, 0) AS first_time_buyers, 
               Ifnull(returned_buyers, 0)   AS returned_buyers 
        FROM   table1 
               LEFT JOIN table2 
                      ON table1.month = table2.month 
        GROUP  BY month 
        UNION ALL 
        SELECT table2.month, 
               Ifnull(first_time_buyers, 0) AS first_time_buyers, 
               Ifnull(returned_buyers, 0)   AS returned_buyers 
        FROM   table2 
               LEFT JOIN table1 
                      ON table2.month = table1.month 
        GROUP  BY month) t 
GROUP  BY month; 

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你希望我们怎样帮助你？显示您的查询、数据和表格。请设置文本格式：这是两个不同的表格吗？您如何识别id为的买家？文本格式为，。请帮帮我！！您是如何创建这两个初始结果的？它们是表格还是查询输出？你能给我一个查询吗？请输入我的答案。看一看。