Clickhouse fields are grouped and aggregated, and SQL is queried according to the granularity of any time period

demand

• Basic data warehousing , You need to do some aggregation according to the fields
• Existing intersection passing data , There are various models , It is necessary to count the total flow and the flow of each model , To return together
• Existing passing data , It needs different granularity according to time , Count the traffic flow , Achieve different time granularity summation ,5 minute 、10 minute 、 Half an hour 、 A month 、 A year will do

solve

Use if and sum

• Mainly used if, The eligible conditions are 1, The nonconformity is 0, Reuse sum Sum up

select
	count(1) as " Total discharge ",
	SUM(if(vehicle_type = 'PEDESTRIAN', 1, 0)) as " Pedestrian flow ",
	SUM(if(vehicle_type = 'NON_MOTORIZED', 1, 0)) as " Non motor vehicle flow ",
	SUM(if(vehicle_type = 'LIGHT_DUTY', 1, 0)) as " Small traffic flow ",
	SUM(if(vehicle_type = 'MEDIAN_SIZED', 1, 0)) as " Medium traffic flow ",
	SUM(if(vehicle_type = 'OVERSIZE', 1, 0)) as " Large traffic flow "
from
	passing_vehicle
where
	exist_time > 0
	and time_stamp > toDateTime('2022-06-30 11:00:00')
	and time_stamp < toDateTime('2022-06-30 15:00:00')
;

Use toStartOfInterval

select
	toStartOfInterval(time_stamp , INTERVAL 30 minute) as half_hour,
	count(1) as " Total discharge ",
	SUM(if(vehicle_type = 'PEDESTRIAN', 1, 0)) as " Pedestrian flow ",
	SUM(if(vehicle_type = 'NON_MOTORIZED', 1, 0)) as " Non motor vehicle flow ",
	SUM(if(vehicle_type = 'LIGHT_DUTY', 1, 0)) as " Small traffic flow ",
	SUM(if(vehicle_type = 'MEDIAN_SIZED', 1, 0)) as " Medium traffic flow ",
	SUM(if(vehicle_type = 'OVERSIZE', 1, 0)) as " Large traffic flow "
from
	passing_vehicle
where
	exist_time > 0
	and time_stamp > toDateTime('2022-06-30 11:00:00')
	and time_stamp < toDateTime('2022-06-30 15:00:00')
group by
	half_hour,
order by
	half_hour;