Question

我有3张桌子

TAble A：

mydate      myid  amount
========================
2016-03-14     5    100

表B：

mydate      myid  amount
========================
2016-03-14     5    90   
2016-03-15     2     50
2016-03-16     1     80

我想将表A和表B连接到一个新的显示结果，如下所示：

mydate      myid  amount
========================
2016-03-14     5    190   
2016-03-15     2     50
2016-03-16     1     80

请帮助

Answer 1

您可以使用UNION ALL“合并”两个表，然后汇总：

SELECT mydate, myid, SUM(amount) AS amount
FROM (SELECT mydate, myid, amount
      FROM table_A
      UNION ALL
      SELECT mydate, myid, amount
      FROM table_B) AS sub
GROUP BY mydate, myid
ORDER BY mydate;

在mysql中连接2个表，其中一个表有更多行并将其加总

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