Question

我有2张桌子

Table 1
date         Tcount
2017-09-04   1
2017-09-04   1
2017-09-05   1
2017-09-03   1

Table 2
date         Tcount
2017-09-05   2
2017-09-02   1

如何使输出如下（与连接mysql或等）????


date         TcountTable1   TcountTable2
2017-09-02   null           1
2017-09-03   1              null
2017-09-04   2              null
2017-09-05   1              2

Answer 1

这相当于其他数据库中的full join（聚合后）。

MySQL不支持full join。您可以使用union all和聚合：

select date, sum(tcount1) as tcount1, sum(tcount2) as tcount2
from ((select date, tcount as tcount1, null as tcount2
       from table1
      ) union all
      (select date, NULL as tcount1, tcount as tcount2
       from table2
      )
     ) tt
group by date;

具有连接输出的MYSQL计数

1 个答案: