如何在PostgreSQL中获取列值的计数

Question

我有两个表第一个是Status，deviceSerial列.Status位于（1,2,3,4,5）中。 我想获得结果作为状态计数

例如，设备一要获取一行中状态1，状态2，状态3，状态4，状态5的记录数量

这是我的第一张桌子

这是我的第二张桌子

我想得到这些记录作为

这是我尝试的代码

Select "deviceSerial",  (select count("statusId")as Permitted from public.scan_track
where "statusId" = 1 group by "statusId"),

(select count("statusId")as IssuedToday from public.scan_track
where "statusId" = 2 group by "statusId"),

(select count("statusId")as PaidForParking from public.scan_track
where "statusId" = 3 group by "statusId"),

(select count("statusId")as InvalidVehicle from public.scan_track
where "statusId" = 4 group by "statusId"),

(select count("statusId")as ExpiredOrNotPaid from public.scan_track
where "statusId" = 5 group by "statusId"),

(select count("statusId")as Failed from public.scan_track
where "statusId" = 6 group by "statusId"),

(select count("statusId")as Other from public.scan_track
where "statusId" = 7 group by "statusId")
from public.scan_track
group by "deviceSerial"

我在这个问题上犯了什么错误，请帮助我

Answer 1

使用透视逻辑：

SELECT
    deviceSerial,
    COUNT(*) FILTER (WHERE statusid = 1) AS Permitted,
    COUNT(*) FILTER (WHERE statusid = 2) AS IssuedToday,
    COUNT(*) FILTER (WHERE statusid = 3) AS PaidForParking,
    COUNT(*) FILTER (WHERE statusid = 4) AS InvalidVehicle,
    COUNT(*) FILTER (WHERE statusid = 5) AS ExpiredOnNotPaid,
    COUNT(*) FILTER (WHERE statusid = 6) AS Failed,
    COUNT(*) FILTER (WHERE statusid = 7) AS Other
FROM scan_track
GROUP BY
    deviceSerial;

Answer 2

您可以在下面尝试使用条件聚合

select deviceserial,
       count(case when statusid=1 then 1 end) as Permitted ,
       count(case when statusid=2 then 1 end) as IssuedToday,
       count(case when statusid=3 then 1 end) as Permitted ,
       count(case when statusid=4 then 1 end) as InvalidVehicle,
       count(case when statusid=5 then 1 end) as ExpiredOrNotPaid ,
       count(case when statusid=6 then 1 end) as Failed ,
       count(case when statusid=7 then 1 end) as Other
from firstTtable
group by deviceserial