我正在尝试efficiency
在我的sql代码中计算,该代码需要除以2个变量vehicle_dispatched
,available_cars
但是对于整个列它返回相同的答案。这是我的SQL代码:
SELECT *,@vehicles_dispatched:=COUNT(DISTINCT v.vehicle_id) AS vehicles_dispatched,
@available_cars:=(SELECT COUNT(vehicle_id) FROM vehicles WHERE company_id=1) AS available_cars,
FORMAT(@vehicles_dispatched / @available_cars,2) AS efficiency
FROM driver_attendance da
LEFT JOIN vehicles v ON v.vehicle_id=da.vehicle_id
LEFT JOIN collection co ON co.driver_attendance_id=da.driver_attendance_id
LEFT JOIN collectible cb ON cb.collectible_id = co.collectible_id
WHERE company_id=1 GROUP BY attendance_date DESC
样本输出:
vehicles_dispatched available_cars efficiency
5 7 0.14
3 7 0.14
6 7 0.14
1 7 0.14
问题是整个列都有相同的答案,而不是对每一行进行除法。
这是更新的查询,它提供了我想要的输出,这一切都要感谢@Ravinder。
SELECT *,FORMAT( vehicle_dispatched / available_cars, 2 ) AS efficiency
FROM(
SELECT da.*,
SUM(CASE WHEN attendance_status = 4 THEN 1 ELSE 0 END) AS total_cars_collectible,
SUM(boundary_payment)+SUM(deficit_payment) AS total_daily_collection,
((SUM(boundary_due)+SUM(boundary_deficit)) - (SUM(boundary_payment)+SUM(deficit_payment))) AS total_short,
@cars_in_maintenance:=(SELECT SUM(DISTINCT(CASE WHEN vehicle_on_duty=2 THEN 1 ELSE 0 END)) AS cars_under_maintenance FROM vehicles WHERE company_id=84) AS cars_in_maintenance,
@vehicle_dispatched:=COUNT(DISTINCT v.vehicle_id) AS vehicle_dispatched,
@available_cars:=(SELECT COUNT(vehicle_id) FROM vehicles WHERE company_id=84) AS available_cars
FROM driver_attendance da
LEFT JOIN vehicles v ON v.vehicle_id = da.vehicle_id
LEFT JOIN collection co ON co.driver_attendance_id = da.driver_attendance_id
LEFT JOIN collectible cb ON cb.collectible_id = co.collectible_id
WHERE v.company_id = 84
GROUP BY da.attendance_date DESC
) AS vehicles_attended
当将诸如count
,max
等的聚合函数与用户定义的变量一起使用时,所产生的行为是未知的。我找不到有关的文档。
一段时间以前,我对SO提出了类似的问题:
...当使用聚合函数(如count,sum,group by)执行类似的语句时,结果模式完全不同.... SQL Fiddle上的示例...
在查询上,您可以首先计算各种值的计数,然后efficiency
在外部查询中进行计算。
select vehicles_dispatched, available_cars
, format( vehicles_dispatched / available_cars, 2 ) as efficiency
from(
select da.*, count( distinct v.vehicle_id ) as vehicles_dispatched
, count( v.vehicle_id ) as available_cars
from driver_attendance da
left join vehicles v on v.vehicle_id = da.vehicle_id
left join collection co on co.driver_attendance_id = da.driver_attendance_id
left join collectible cb on cb.collectible_id = co.collectible_id
where v.company_id = 1
group by da.attendance_date desc;
) as vehicles_attended
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