postgres中的时间戳比较

Question

我有两个具有相似数据的查询（一个与上一时期有关，另一个与当前时期有关）。我需要在 kendo 折线图中显示它。我该怎么做**

select date_trunc('hour' , "CreateDateTime"::TIMESTAMP) as c, 
       count(1) as d 
from "ROBOT" 
where "CreateDateTime"::TIMESTAMP between '2018-04-01' and '2018-04-22' 
group by date_trunc('hour', "CreateDateTime"::TIMESTAMP) 

UNION ALL

select date_trunc('hour' , "CreateDateTime"::TIMESTAMP) as a, 
count(1) as b 
from "ROBOT" 
where "CreateDateTime"::TIMESTAMP between '2018-05-01' and '2018-05-22' 
group by date_trunc('hour', "CreateDateTime"::TIMESTAMP);

Answer 1

您似乎想要并排计算两个月的每小时计数。假设这是正确的，你想要这样的东西：

select date_part('hour', "CreateDateTime"::TIMESTAMP) as hour,
       sum(case when "CreateDateTime"::TIMESTAMP between '2018-04-01' and '2018-04-22' then 1 else 0 end) as apr,
       sum(case when "CreateDateTime"::TIMESTAMP between '2018-05-01' and '2018-05-22' then 1 else 0 end) as may
from "ROBOT"
where "CreateDateTime"::TIMESTAMP between '2018-04-01' and '2018-04-22'
   or "CreateDateTime"::TIMESTAMP between '2018-05-01' and '2018-05-22'
group by 1;

当您想从具有不同条件的相同数据生成多个总和时，sum(case...) 模式是一个很好的选择。

postgres中的时间戳比较

Timestamps comparison in postgres

postgresql

ajax

jquery

pgadmin

kendo-ui