mysql - sql合并两个查询结果

Question

使用 xampp mysql
q1:

SELECT truckid, count(deliveryid) 
  FROM `delivery` 
 WHERE year(deliverydate)=2019 and month(deliverydate)=1 
 GROUP BY truckid

q2:

 SELECT truckid,count(deliverid) 
   FROM `delivery2` 
  WHERE YEAR(ddate)=2019 and MONTH(ddate)=1 
  GROUP BY truckid

我正在尝试获得一页有 4 列的结果，以便我可以在它们之间进行比较

我上个月已经完成了，我想我使用了左连接，但我现在似乎无法让它工作:(

帮助。

Answer 1

您可以使用union all并进行条件聚合:

select truckid, 
       sum( tbl = 'delivery' ) as delivery_count,
       sum( tbl = 'delivery2' ) as delivery2_count
from (select truckid, deliveryid, 'delivery' as tbl
      from delivery
      where year(deliverydate) = 2019 and month(deliverydate) = 1
      union all
      select truckid, deliverid, 'delivery2'
      from delivery2
      where YEAR(ddate) = 2019 and MONTH(ddate) = 1
     ) t
group by truckid;