Rush Hour table for every day in a month MySQL - mysql

Question

I'm trying to make a query to get rush hours for everyday on a specific month.
The table I have looks like this:
id idproduct created_at
1 021354684 2011-10-01 20:25:48
2 033546835 2011-10-01 20:30:15
3 055965654 2011-10-01 20:45:20
4 012975343 2011-10-02 14:03:36
5 021354684 2011-10-02 15:55:48
6 033546835 2011-10-02 16:30:15
7 055965654 2011-10-02 16:45:20
8 012975343 2011-10-02 18:53:36
9 021354684 2011-10-03 08:55:48
10 033546835 2011-10-03 09:30:15
11 055965654 2011-10-03 14:03:20
12 012975343 2011-10-03 14:03:36
What I try to get is something like this...:
day rush_hour number_of_rows
1 20:00 3
2 16:00 5
3 14:00 4
Is it possible to get a table like this? can you guys help me?
I made a mistake, sorry for this. The number of rows should be the total of items sold that day, not in that hour :( sorry.

Answer 1

http://sqlfiddle.com/#!2/5b87b/7
First, count every day's every hour's count (into a view, because we will use it twice below):
CREATE VIEW hours AS
SELECT
DATE( created_at ) AS d,
HOUR( created_at ) AS h,
COUNT(*) AS c
FROM item
GROUP BY DATE(created_at), HOUR(created_at);
Final query:
SELECT
hours.d AS `day`,
hours.h AS `rush_hour`,
hours.c AS `count`
-- get the max count for every day
FROM (
SELECT
d, -- the day
MAX(c) as c -- the count
FROM hours
GROUP BY d
) AS maxc
-- find the actual hour(s) with the max count for every day:
INNER JOIN hours ON hours.c = maxc.c
AND hours.d = maxc.d;

Answer 2

You're going to want to look at the MySQL Date Functions, they offer you some help with this
SELECT
day(created_at) as day,
hour(created_at) as rush_hour,
count(1) as num_rows
FROM item
GROUP BY
day(created_at), hour(created_at)
http://sqlfiddle.com/#!2/62a15/2/0

Answer 3

Try this:
SELECT dayofyear(created_at) as day, hour(created_at) as rush_hour, count(*) as number_of_rows
FROM table
GROUP BY dayofyear(created_at), hour(created_at);

Answer 4

Here it is without making a view:
SELECT ddd.day, eee.rush_hour, ddd.maxo
FROM
(select day, max(num_rows) as maxo from (
SELECT
day(created_at) as day,
hour(created_at) as rush_hour,
count(1) as num_rows
FROM item
GROUP BY
day(created_at), hour(created_at)
) as groupo group by day) as ddd
LEFT JOIN
(SELECT
day(created_at) as day,
hour(created_at) as rush_hour,
count(1) as num_rows
FROM item
GROUP BY
day(created_at), hour(created_at)
) as eee on ddd.day=eee.day and ddd.maxo=eee.num_rows
I could imagine it being formatted more nicely or having more relevant aliases, but there's just so much subselecting going on here.
And thanks SQLfiddlers for putting the data there.
And I think that if you have two hours tied for the highest number of whatever it is you are counting, they both will show up, so you'll get two (or more) records returned for that day of the month.