计算一天中每个小时的 SQL table 中的不同值

Question

我有一个 table 看起来像这样：

ID    TimeStamp    CarNumber
1    2018 14:05:32    433
2    2018 14:13:52    420
3    2018 14:55:14    433
4    2018 15:12:03    420
5    2018 16:15:55    570

我必须得到一天中每个小时的不同车号的数量，所以我现在做的是运行每个小时单独的命令：

SELECT DISTINCT CarNumber
FROM Cars
WHERE TimeStamp BETWEEN '2018 14:00:00' AND '2018 15:00:00'

有没有办法构建一个 table 来自动在一天中的每个小时执行此操作？预期输出：

Hour    NumberOfCars    CarNumbers
0       0               0
...
14      2               433, 420
15      1               420
16      1               570
...

Answer 1

您可以按日期和时间汇总：

select cast(timestamp as date) as thedate,
       datepart(hour, timestamp) as thehour,
       count(distinct CarNumber) as num_cars
from cars
group by cast(timestamp as date), datepart(hour, timestamp)
order by thedate, thehour;

如果您只需要一个日期的结果，您可以添加 where 子句。如果您希望在多天内汇总结果，请从逻辑中删除 thedate：

select datepart(hour, timestamp) as thehour,
       count(distinct CarNumber) as num_cars
from cars
group by datepart(hour, timestamp)
order by thehour;

Answer 2

像下面这样尝试。从日期时间列中提取小时数并按

分组使用

 select convert(date,TimeStamp),
 DATEPART(HOUR, TimeStamp) ,
 count(distinct CarNumber) numofcars
 from Cars 
 group by convert(date,TimeStamp),DATEPART(HOUR, TimeStamp)

计算一天中每个小时的 SQL table 中的不同值

Count distinct values in an SQL table for each hour in a day

sql

sql-server-2008