MySQL basic query (single table)

Basic format:

select * from table name where condition

1. Use count(*) to query the number

select 车牌,count(*) as count from 小数据1 group by 车牌 ORDER BY count DESC

2. From a column containing date and time

Extract the date with DATE_FORMAT(time,'%Y-%c-%d')

Extract the month with DATE_FORMAT(entry charging time, '%Y-%m') = '2017-08'

select DATE_FORMAT(入口收费时间,'%Y-%m-%d') 起始日期,count(*) 数目 from 小数据1 
WHERE DATE_FORMAT(入口收费时间, '%Y-%m') = '2017-08' group by 起始日期;

or MONTH(DATE_FORMAT(entry charging time, '%Y-%m-%d')) = 8

SELECT * FROM 小数据1 WHERE MONTH(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) = 8 AND DAYOFWEEK(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) = 3;

Extract the date of each day of the month using day(DATE_FORMAT(entry charging time, '%Y-%m-%d'))

select day(DATE_FORMAT(入口收费时间, '%Y-%m-%d'))日期, count(*) 
from 小数据1 WHERE (MONTH(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) = 8) 
group by 日期

Extract the week using DAYOFWEEK(DATE_FORMAT(entry charging time, '%Y-%m-%d'))

SELECT DAYOFWEEK(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) 星期,count(*)交通量 
FROM airportroad_utf8 
WHERE MONTH(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) = 8 GROUP BY 星期

Use DATE_FORMAT (entry charging time, "%H") to extract time

select *,count(*) as 数量 from airportroad_utf8
WHERE (DATE_FORMAT(入口收费时间,"%H")>7 and (DATE_FORMAT(入口收费时间,"%H")<9))
)

Extract the amount of data at intervals of five minutes

SELECT time, COUNT( * ) AS num 
FROM
	(
	SELECT *,
		DATE_FORMAT(
			concat( date( 入口收费时间 ), ' ', HOUR (入口收费时间 ), ':', floor( MINUTE ( 入口收费时间 ) / 5 ) * 5 ),
			'%Y-%m-%d %H:%i' 
		) AS time 
	FROM airportroad_utf8 where (MONTH(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) = 8) and (起始站点 = '山前') 
)	a 
GROUP BY DATE_FORMAT( time, '%Y-%m-%d %H:%i' ) 
ORDER BY time;

3. To get the speed, you need to calculate (km 1000 3.6/TIME_TO_SEC(TIMEDIFF( 出口收费时间, 入口收费时间))) as speed

4. Get grouped results with group by

5. Use case when to get the result of partition

select 速度段,count(*) as 数量 from(
select (公里*1000*3.6/TIME_TO_SEC(TIMEDIFF(`出口收费时间`,`入口收费时间` ))) as 速度,
case
when 公里*1000*3.6/TIME_TO_SEC(TIMEDIFF(`出口收费时间`,`入口收费时间` )) between 0 and 20 then '0-20'
when 公里*1000*3.6/TIME_TO_SEC(TIMEDIFF(`出口收费时间`,`入口收费时间` )) between 20 and 40 then '20-40'
when 公里*1000*3.6/TIME_TO_SEC(TIMEDIFF(`出口收费时间`,`入口收费时间` )) between 40 and 60 then '40-60'
when 公里*1000*3.6/TIME_TO_SEC(TIMEDIFF(`出口收费时间`,`入口收费时间` )) between 60 and 80 then '60-80'
when 公里*1000*3.6/TIME_TO_SEC(TIMEDIFF(`出口收费时间`,`入口收费时间` )) > 80 then '80+'
end as 速度段
FROM airportroad_utf8
WHERE (MONTH(DATE_FORMAT(入口收费时间, '%Y-%m-%d')) = 8) and  ((DAYOFWEEK(DATE_FORMAT(入口收费时间, '%Y-%m-%d'))=1) or  (DAYOFWEEK(DATE_FORMAT(入口收费时间, '%Y-%m-%d'))=7))
and (DATE_FORMAT(入口收费时间,"%H")>17 and (DATE_FORMAT(入口收费时间,"%H")<19))
)  
a GROUP BY 速度段

When you use case when, you actually create a virtual table and query in this virtual table. Don’t forget the latter a, otherwise an error will be reported.

MySQL basic query (single table)

MySQL basic query (single table)

Guess you like