Group by half hour interval - mysql
I was lucky enough to find this awesome piece of code on Stack Overflow, however I wanted to change it up so it showed each half hour instead of every hour, but messing around with it, only caused me to ruin the query haha.
This is the SQL:
SELECT CONCAT(HOUR(created_at), ':00-', HOUR(created_at)+1, ':00') as hours,
COUNT(*)
FROM urls
GROUP BY HOUR(created_at)
ORDER BY HOUR(created_at) ASC
How would I go about getting a result every half an hour? :)
Another thing, is that, if it there is half an hour with no results, I would like it to return 0 instead of just skipping that step. It looks kinda of weird win I do statistics over the query, when it just skips an hour because there were none :P
If the format isn't too important, you can return two columns for the interval. You might even just need the start of the interval, which can be determined by:
date_format(created_at - interval minute(created_at)%30 minute, '%H:%i') as period_start
the alias can be used in GROUP BY and ORDER BY clauses. If you also need the end of the interval, you will need a small modification:
SELECT
date_format(created_at - interval minute(created_at)%30 minute, '%H:%i') as period_start,
date_format(created_at + interval 30-minute(created_at)%30 minute, '%H:%i') as period_end,
COUNT(*)
FROM urls
GROUP BY period_start
ORDER BY period_start ASC;
Of course you can also concatenate the values:
SELECT concat_ws('-',
date_format(created_at - interval minute(created_at)%30 minute, '%H:%i'),
date_format(created_at + interval 30-minute(created_at)%30 minute, '%H:%i')
) as period,
COUNT(*)
FROM urls
GROUP BY period
ORDER BY period ASC;
Demo: http://rextester.com/RPN50688
Another thing, is that, if it there is half an hour with no results, I
would like it to return 0
If you use the result in a procedural language, you can initialize all 48 rows with zero in a loop and then "inject" the non-zero rows from the result.
However - If you need it to be done in SQL, you will need a table for a LEFT JOIN with at least 48 rows. That could be done inline with a "huge" UNION ALL statement, but (IMHO) it would be ugly. So I prefer to have sequence table with one integer column, which can be very usefull for reports. To create that table I usually use the information_schema.COLUMNS, since it is available on any MySQL server and has at least a couple of hundreds rows. If you need more rows - just join it with itself.
Now let's create that table:
drop table if exists helper_seq;
create table helper_seq (seq smallint auto_increment primary key)
select null
from information_schema.COLUMNS c1
, information_schema.COLUMNS c2
limit 100; -- adjust as needed
Now we have a table with integers from 1 to 100 (though right now you only need 48 - but this is for demonstration).
Using that table we can now create all 48 time intervals:
select time(0) + interval 30*(seq-1) minute as period_start,
time(0) + interval 30*(seq) minute as period_end
from helper_seq s
where s.seq <= 48;
We will get the following result:
period_start | period_end
00:00:00 | 00:30:00
00:30:00 | 01:00:00
...
23:30:00 | 24:00:00
Demo: http://rextester.com/ISQSU31450
Now we can use it as a derived table (subquery in FROM clause) and LEFT JOIN your urls table:
select p.period_start, p.period_end, count(u.created_at) as cnt
from (
select time(0) + interval 30*(seq-1) minute as period_start,
time(0) + interval 30*(seq) minute as period_end
from helper_seq s
where s.seq <= 48
) p
left join urls u
on time(u.created_at) >= p.period_start
and time(u.created_at) < p.period_end
group by p.period_start, p.period_end
order by p.period_start
Demo: http://rextester.com/IQYQ32927
Last step (if really needed) is to format the result. We can use CONCAT or CONCAT_WS and TIME_FORMAT in the outer select. The final query would be:
select concat_ws('-',
time_format(p.period_start, '%H:%i'),
time_format(p.period_end, '%H:%i')
) as period,
count(u.created_at) as cnt
from (
select time(0) + interval 30*(seq-1) minute as period_start,
time(0) + interval 30*(seq) minute as period_end
from helper_seq s
where s.seq <= 48
) p
left join urls u
on time(u.created_at) >= p.period_start
and time(u.created_at) < p.period_end
group by p.period_start, p.period_end
order by p.period_start
The result would look like:
period | cnt
00:00-00:30 | 1
00:30-01:00 | 0
...
23:30-24:00 | 3
Demo: http://rextester.com/LLZ41445
Switch to seconds.
Do arithmetic to get a number for each unit of time (using 30*60 for half-hour, in your case)
Have a table of consecutive numbers.
Use LEFT JOIN to get even missing units of time.
Do the GROUP BY.
Convert back from units of time to actual time -- for display.
(Steps 3 and 4 are optional. The question says "every", so I assume they are needed.)
Steps 1 and 2 are embodied in something like
FLOOR(UNIX_TIMESTAMP(created_at) / (30*60))
For example:
mysql> SELECT NOW(), FLOOR(UNIX_TIMESTAMP(NOW()) / (30*60));
+---------------------+----------------------------------------+
| NOW() | FLOOR(UNIX_TIMESTAMP(NOW()) / (30*60)) |
+---------------------+----------------------------------------+
| 2018-03-02 08:24:48 | 844448 |
+---------------------+----------------------------------------+
Step 3 is needs to be done once and kept in a permanent table. Or, if you have MariaDB, use a "seq" pseudo-table; for example `seq_844448_to_900000 would dynamically give a table that would reach pretty far into the future.
Step 6 example:
mysql> SELECT DATE_FORMAT(FROM_UNIXTIME((844448) * 30*60), "%b %d %h:%i");
+-------------------------------------------------------------+
| DATE_FORMAT(FROM_UNIXTIME((844448) * 30*60), "%b %d %h:%i") |
+-------------------------------------------------------------+
| Mar 02 08:00 |
+-------------------------------------------------------------+
+---------------------------------------------------------------+
| DATE_FORMAT(FROM_UNIXTIME((844448+1) * 30*60), "%b %d %h:%i") |
+---------------------------------------------------------------+
| Mar 02 08:30 |
+---------------------------------------------------------------+
Well, this could be a bit verbose but it works:
SELECT hours, SUM(count) as count FROM (
SELECT CONCAT(HOUR(created_at), ':', LPAD(30 * FLOOR(MINUTE(created_at)/30), 2, '0'), '-',
HOUR(DATE_ADD(created_at, INTERVAL 30 minute)), ':', LPAD(30 * FLOOR(MINUTE(DATE_ADD(created_at, INTERVAL 30 minute))/30), 2, '0')) as hours,
COUNT(*) as count
FROM urls
GROUP BY HOUR(created_at), FLOOR(MINUTE(created_at)/30)
UNION ALL
SELECT '00:00-00:30'as hours, 0 as count UNION ALL SELECT '00:30-01:00'as hours, 0 as count UNION ALL
SELECT '01:00-01:30'as hours, 0 as count UNION ALL SELECT '01:30-02:00'as hours, 0 as count UNION ALL
SELECT '02:00-02:30'as hours, 0 as count UNION ALL SELECT '02:30-03:00'as hours, 0 as count UNION ALL
SELECT '03:00-03:30'as hours, 0 as count UNION ALL SELECT '03:30-04:00'as hours, 0 as count UNION ALL
SELECT '04:00-04:30'as hours, 0 as count UNION ALL SELECT '04:30-05:00'as hours, 0 as count UNION ALL
SELECT '05:00-05:30'as hours, 0 as count UNION ALL SELECT '05:30-06:00'as hours, 0 as count UNION ALL
SELECT '06:00-06:30'as hours, 0 as count UNION ALL SELECT '06:30-07:00'as hours, 0 as count UNION ALL
SELECT '07:00-07:30'as hours, 0 as count UNION ALL SELECT '07:30-08:00'as hours, 0 as count UNION ALL
SELECT '08:00-08:30'as hours, 0 as count UNION ALL SELECT '08:30-09:00'as hours, 0 as count UNION ALL
SELECT '09:00-09:30'as hours, 0 as count UNION ALL SELECT '09:30-10:00'as hours, 0 as count UNION ALL
SELECT '10:00-10:30'as hours, 0 as count UNION ALL SELECT '10:30-11:00'as hours, 0 as count UNION ALL
SELECT '11:00-11:30'as hours, 0 as count UNION ALL SELECT '11:30-12:00'as hours, 0 as count UNION ALL
SELECT '12:00-12:30'as hours, 0 as count UNION ALL SELECT '12:30-13:00'as hours, 0 as count UNION ALL
SELECT '13:00-13:30'as hours, 0 as count UNION ALL SELECT '13:30-14:00'as hours, 0 as count UNION ALL
SELECT '14:00-14:30'as hours, 0 as count UNION ALL SELECT '14:30-15:00'as hours, 0 as count UNION ALL
SELECT '15:00-15:30'as hours, 0 as count UNION ALL SELECT '15:30-16:00'as hours, 0 as count UNION ALL
SELECT '16:00-16:30'as hours, 0 as count UNION ALL SELECT '16:30-17:00'as hours, 0 as count UNION ALL
SELECT '17:00-17:30'as hours, 0 as count UNION ALL SELECT '17:30-18:00'as hours, 0 as count UNION ALL
SELECT '18:00-18:30'as hours, 0 as count UNION ALL SELECT '18:30-19:00'as hours, 0 as count UNION ALL
SELECT '19:00-19:30'as hours, 0 as count UNION ALL SELECT '19:30-20:00'as hours, 0 as count UNION ALL
SELECT '20:00-20:30'as hours, 0 as count UNION ALL SELECT '20:30-21:00'as hours, 0 as count UNION ALL
SELECT '21:00-21:30'as hours, 0 as count UNION ALL SELECT '21:30-22:00'as hours, 0 as count UNION ALL
SELECT '22:00-22:30'as hours, 0 as count UNION ALL SELECT '22:30-23:00'as hours, 0 as count UNION ALL
SELECT '23:00-23:30'as hours, 0 as count UNION ALL SELECT '23:30-00:00'as hours, 0 as count
) AS T
GROUP BY hours ORDER BY hours;
The most difficult part of your query is output of statistics for intervals that don't have any hits. SQL is all about querying and aggregating existing data; selecting or aggregating the data missing in the table is quite unordinary task. That's why, like Wolph stated in comments, there is no pretty solution for this task.
I solved this problem by explicitly selecting all half intervals of the day. This solution could be used if number of intervals is limited like in your case. This will not work however if you aggregate by different days from long period of time.
I'm not a fan of this query but I can't propose anything better. More elegant solution could be achieved with stored procedure with a loop, but seems like you want to solve it with raw SQL query.
You can add some math to calculate 48 intervals instead of 24 and put it into another field by which you're going to group and sort.
SELECT HOUR(created_at)*2+FLOOR(MINUTE(created_at)/30) as interval48,
if(HOUR(created_at)*2+FLOOR(MINUTE(created_at)/30) % 2 =0,
CONCAT(HOUR(created_at), ':00-', HOUR(created_at), ':30'),
CONCAT(HOUR(created_at), ':30-', HOUR(created_at)+1, ':00')
) as hours,
count(*)
FROM urls
GROUP BY HOUR(created_at)*2+FLOOR(MINUTE(created_at)/30)
ORDER BY HOUR(created_at)*2+FLOOR(MINUTE(created_at)/30) ASC
Example of result:
0 0:00-0:30 2017
1 0:30-1:00 1959
2 1:30-2:00 1830
3 1:30-2:00 1715
4 2:30-3:00 1679
5 2:30-3:00 1688
The result of original query posted by Jazerix was:
0:00-1:00 3976
1:00-2:00 3545
2:00-3:00 3367
A different Approach without creating additional tables. May look like a hack though :-)
Step 1 : Generate a Time Table Dynamically
Assumption : INFORMATION_SCHEMA DB is avaialble and has a table COLLATIONS which normally has more than 100 records. You can use any table which has minimum 48 records
Query :
SELECT #time fromTime, ADDTIME(#time, '00:29:00') toTime,
#time := ADDTIME(#time, '00:30:00')
FROM information_schema.COLLATIONS
JOIN (SELECT #time := TIME('00:00:00')) a
WHERE #time < '24:00:00'
Above query will give a table with from time and to time with an interval of 30 minutes.
Step 2 : Use the first query to generate required result joining urls table
Query :
SELECT CONCAT(fromTime, '-', toTime) AS halfHours, COUNT(created_at)
FROM
(SELECT #time fromTime, ADDTIME(#time, '00:29:00') toTime, #time := ADDTIME(#time, '00:30:00')
FROM information_schema.COLLATIONS
JOIN (SELECT #time := TIME('00:00:00')) a
WHERE #time < '24:00:00'
) timeTable
LEFT JOIN urls ON HOUR(created_at) BETWEEN HOUR(fromTime) AND HOUR(toTime)
AND MINUTE(created_at) BETWEEN MINUTE(fromTime) AND MINUTE(toTime)
GROUP BY fromTime
SQLFiddle
I hope this will work for,
SELECT
#sTime:= CONCAT(HOUR(created_at),":",
(CASE WHEN MINUTE(created_at) > 30 THEN 30 ELSE 0 END)) as intVar,
(CONCAT(
AddTime(#sTime, '00:00:00'),
' to ',
AddTime(#sTime, '00:30:00')
)) as timeInterval,
COUNT(*) FROM urls
GROUP BY
(CONCAT(HOUR(created_at),":",(CASE WHEN MINUTE(created_at) > 30 THEN 30 ELSE 0 END)))
ORDER BY HOUR(created_at) ASC
Simply convert to sec and divide by 30 mins(1800secs). And to verify i used min, max on timestamp.
SELECT concat(TIME_FORMAT(min(created_at),"%H:%i")," - ", TIME_FORMAT(max(created_at),"%H:%i")) as hours,
COUNT(*)
FROM urls
GROUP BY FLOOR(TIME_TO_SEC(created_at)/1800)
ORDER BY HOUR(created_at) ASC
Related
A query for getting results separated by a date gap
ID TIMESTAMP 1 2020-01-01 12:00:00 2 2020-02-01 12:00:00 3 2020-05-01 12:00:00 4 2020-06-01 12:00:00 5 2020-07-01 12:00:00 I am looking for a way to get records in a MySQL database that are within a certain range of each other. In the above example, notice that there is a month between the first two records, then a three month gap, before we see another three records with a month between. What is a way to group these into two result sets, so I will get Ids 1, 2 and 3, 4, 5 A solution using days would be probably work the best as thats easier to modify.
You can use lag() and then logic to see where a gap is big enough to start a new set of records. A cumulative sum gives you the groups you want: select t.*, sum(case when prev_timestamp >= timestamp - interval 1 month then 0 else 1 end) over (order by timestamp) as grouping from (select t.*, lag(timestamp) over (order by timestamp) as prev_timestamp from t ) t; If you want to summarize this with a start and end date: select min(timestamp), max(timestamp) from (select t.*, sum(case when prev_timestamp >= timestamp - interval 1 month then 0 else 1 end) over (order by timestamp) as grouping from (select t.*, lag(timestamp) over (order by timestamp) as prev_timestamp from t ) t ) t group by grouping;
For example, the following query: select group_concat(ID) from ( select w1.ID,w1.TS,w2.ID flag from work1 w1 left outer join work1 w2 on timestampdiff(month,w2.TS,w1.TS)=1 order by w1.ID ) w group by case when flag is null then #str:=ID else #str end See db fiddle
Getting all previous records of table by date MySQL
My table currently has 21000 records, it's daily updated and almost 300 entries are inserted. Now, what I want is to have a query which will fetch the counts of elements that my table had for the previous 10 days, so it returns: 26000 21300 21000 etc Right now, I wrote this: "SELECT COUNT(*) from tbl_task where `task_start_time` < '2020-12-01'" And it returns 21000 but only for 1 day. I want by query to return records according to 10 days. However, this does it for only 1 day. edit : database flavor is mysql and date column is date not datetime
The most efficient method may be aggregation and cumulative sums: select date(task_start_time) as dte, count(*) as cnt_on_day, sum(count(*)) over (order by date(task_start_time)) as running_cnt from tbl_task group by dte order by dte desc limit 10; This returns the last 10 days in the data. You can easily adjust to more days if you like -- in fact all of them -- without much trouble.
I don't know if I'm wrong, but could you not simple add a GROUP BY - statement? Like: "SELECT COUNT(*) from tbl_task where `task_start_time` < '2020-12-01' GROUP BY task_start_time" EDIT: This should only work if task_start_time is a date, not if it is a datetime EDIT2: If it is a datetime you could use the date function: SELECT COUNT(*) from tbl_task where `task_start_time` < '2020-12-01' GROUP BY DATE(task_start_time)
You can use UNION ALL and date arithmetic. SELECT count(*) FROM tbl_task WHERE task_start_time < current_date UNION ALL SELECT count(*) FROM tbl_task WHERE task_start_time < date_sub(current_date, INTERVAL 1 DAY) ... UNION ALL SELECT count(*) FROM tbl_task WHERE task_start_time < date_sub(current_date, INTERVAL 9 DAY); Edit: You might also join a derived table that uses FROM-less SELECTs and UNION ALL to get the days to look back and then aggregate. This might be a little easier to construct dynamically. (But it may be slower I suspect.) SELECT count(*) FROM (SELECT 0 x UNION ALL SELECT 1 ... UNION ALL SELECT 9) INNER JOIN tbl_task t ON t.task_start_time < date_sub(current_date, INTERVAL x.x DAY) GROUP BY x.x; In MySQL version 8+ you can even use a recursive CTE to construct the table with the days. WITH RECURSIVE x AS ( SELECT 0 x UNION ALL SELECT x + 1 FROM x WHERE x + 1 < 10 ) SELECT count(*) FROM x INNER JOIN tbl_task t ON t.task_start_time < date_sub(current_date, INTERVAL x.x DAY) GROUP BY x.x;
Elapsed Time Between Two Dates for specified time range
I have a MYSQL table with a TIMESTAMP column 'Start' and a TIMESTAMP column 'End'. I want to return the number of minutes between the start and the end (End is always after than Start). Usually I'd just use 'TIMESTAMPDIFF()' but this time I need to get the minutes from 9am until 22pm, of each day in that date range.
If a row has a Start '2017-01-01 07:15:00' and an End of '2017-01-02 11:30:00' - the elapsed time should be 15.5 hours (930 minutes).
I'm having trouble coming up with a decent way of doing this and my searching online hasn't found quite what I'm looking for. Can someone help me along?
Edit:
CREATE TABLE date_ranges (
Start TIMESTAMP,
End TIMESTAMP
);
INSERT INTO date_ranges VALUES('2017-01-01 07:15:00','2017-01-02 11:30:00');
I came up with this:
SELECT Start, End, TIMESTAMPDIFF(MINUTE, Start, End) AS MinutesElapsed
FROM date_ranges;
I'm missing the part where the time in minutes is calculated only in the specified time range (9am until 22pm). Any ideas?
Here you go: SELECT t1, t2, (TIMESTAMPDIFF(MINUTE, t1, t2) - TIMESTAMPDIFF(DAY, t1, t2)*660) FROM (SELECT CASE WHEN t1 < STR_TO_DATE(concat(date_format(t1, '%Y-%m-%d'), ' 09:00:00'), '%Y-%m-%d %h:%i:%s') THEN STR_TO_DATE(concat(date_format(t1, '%Y-%m-%d'), ' 09:00:00'), '%Y-%m-%d %h:%i:%s') ELSE t1 END AS t1 FROM test) test1, (SELECT CASE WHEN t2 > STR_TO_DATE(concat(date_format(t2, '%Y-%m-%d'), ' 22:00:00'), '%Y-%m-%d %h:%i:%s') THEN STR_TO_DATE(concat(date_format(t2, '%Y-%m-%d'), ' 22:00:00'), '%Y-%m-%d %h:%i:%s') ELSE t2 END AS t2 FROM test) test2; 660 = number of minutes between 22:00 and 09:00 (11 hours) Here's the SQL Fiddle.
It's not very concise, but this should give you the results you want: select started_at,ended_at, (case when date(ended_at) = date(started_at) then timestampdiff( minute, greatest(started_at,concat(date(started_at),' 09:00:00')), least(ended_at,concat(date(ended_at),' 22:00:00')) ) else timestampdiff( minute, least(greatest(started_at,concat(date(started_at),' 09:00:00')),concat(date(started_at),' 22:00:00')), concat(date(started_at),' 22:00:00') ) + timestampdiff( minute, concat(date(ended_at),' 09:00:00'), greatest(least(ended_at,concat(date(ended_at),' 22:00:00')),concat(date(ended_at),' 09:00:00')) ) + ((datediff(ended_at,started_at)-1)*780) end) as total_minutes from your_table;
--Generating all dates in 2017. CREATE TABLE CALENDAR AS --Use a different table name if CALENDAR already exists SELECT '2017-12-31 09:00:00' - INTERVAL c.number DAY AS start_datetime,'2017-12-31 22:00:00' - INTERVAL c.number DAY AS end_datetime FROM (SELECT singles + tens + hundreds number FROM (SELECT 0 singles UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 ) singles JOIN (SELECT 0 tens UNION ALL SELECT 10 UNION ALL SELECT 20 UNION ALL SELECT 30 UNION ALL SELECT 40 UNION ALL SELECT 50 UNION ALL SELECT 60 UNION ALL SELECT 70 UNION ALL SELECT 80 UNION ALL SELECT 90 ) tens JOIN (SELECT 0 hundreds UNION ALL SELECT 100 UNION ALL SELECT 200 UNION ALL SELECT 300 UNION ALL SELECT 400 UNION ALL SELECT 500 UNION ALL SELECT 600 UNION ALL SELECT 700 UNION ALL SELECT 800 UNION ALL SELECT 900 ) hundreds ORDER BY number DESC) c WHERE c.number BETWEEN 0 and 364 ; --End of table creation --Actual query begins here SELECT D.`START`, D.`END`, SUM(TIMESTAMPDIFF(MINUTE,GREATEST(D.`START`,C.START_DATETIME), LEAST(D.`END`,C.END_DATETIME))) AS TOTAL_TIME FROM CALENDAR C LEFT JOIN DATE_RANGES D ON DATE(C.START_DATETIME) >= DATE(D.`START`) AND DATE(C.START_DATETIME) <= DATE(D.`END`) WHERE D.`START` IS NOT NULL AND D.`END` IS NOT NULL GROUP BY D.`START`, D.`END` ; Construct a calendar table with a dates for a specified number of years. Each date having a start time of 09:00 and an end time of 22:00. Left join on this table to get one row per date from the date ranges table. Sum up the differences each day to get the total time worked. Sample Demo
Day 1 Day 2 Day 3 |--********--|--********--|--********--| |__________________________| The question, IMHO is to know how many minutes the first day, and how many minutes the last day, the intermediate days have 780 minutes. I've used a subquery just to help in the intermediate calculations. select if(hour(t1) < 9, date(t1) + interval 9 hour , t1) as tIni1, date(t1) + interval 22 hour as tFin1, date(t2) + interval 9 hour as tIni2, if(hour(t2) > 22, date(t2) + interval 22 hour, t2) as tFin2, TIMESTAMPDIFF(day, date(t1), date(t2)) numDays from tdt tIni1 and tFin1 is the period of the first day, and tIni2, tFin2 the period of the last day, obviously first and last day can be the same. Then calculate minutes of first day + minutes of second day + 780 minutes for every intermediate day. select numDays, tIni1, tFin1, tIni2, tFin2, if (numDays = 0, TIMESTAMPDIFF(minute, tIni1, tFin2), TIMESTAMPDIFF(minute, tIni1, tFin1) + TIMESTAMPDIFF(minute, tIni2, tFin2) + (numDays - 1) * 780 ) as Minutes from ( select if(hour(t1) < 9, date(t1) + interval 9 hour , t1) as tIni1, date(t1) + interval 22 hour as tFin1, date(t2) + interval 9 hour as tIni2, if(hour(t2) > 22, date(t2) + interval 22 hour, t2) as tFin2, TIMESTAMPDIFF(day, date(t1), date(t2)) numDays from tdt ) ti ; Try it here: http://rextester.com/GDHAB78973
MySQL gett rows from last week with their day name
I am having trouble with a query. This is taken from a similar query where i count number of rows per month. I want to count all rows for each day of the last week and display the day name and a count. If there are no rows for that day, display zero. I know the UNIONS won't work but i don't know what to replace it with. At the moment it get the last 7 days but the day name is NULL SELECT DAYNAME(STR_TO_DATE(Days.ID, '%a')) AS `day`, COUNT(`returns`.list_date) AS `total` FROM ( SELECT 1 as ID UNION SELECT 2 as ID UNION SELECT 3 as ID UNION SELECT 4 as ID UNION SELECT 5 as ID UNION SELECT 6 as ID UNION SELECT 7 as ID ) as Days WHERE (list_date >= DATE_SUB(NOW(), INTERVAL 1 WEEK)) GROUP BY Days.id UPDATE: I have created a SQL fiddle showing the code output from #Gordon Linoff answer below which doesn't get the counted rows http://sqlfiddle.com/#!9/969463/1
One method for doing what you want is a LEFT JOIN: SELECT DAYNAME(DATE_SUB(CURDATE(), INTERVAL Days.n DAY)) AS `day`, COUNT(r.list_date) AS `total` FROM (SELECT 1 as n UNION ALL SELECT 2 as n UNION ALL SELECT 3 as n UNION ALL SELECT 4 as n UNION ALL SELECT 5 as n UNION ALL SELECT 6 as n UNION ALL SELECT 7 as n ) Days LEFT JOIN returns r ON r.list_date = DATE_SUB(CURDATE(), INTERVAL Days.n DAY)) GROUP BY Days.n ORDER BY Days.n; Some notes: Use UNION ALL instead of UNION, unless you have a good reason for incurring the overhead of removing duplicates. This assumes that returns.list_date is actually a date, because it uses = rather than >=. The use of now() and >= is a bit confusing, because now() has a time component, which you generally want to ignore.
Find number of "active" rows each month for multiple months in one query
I have a mySQL database with each row containing an activate and a deactivate date. This refers to the period of time when the object the row represents was active. activate deactivate id 2015-03-01 2015-05-10 1 2013-02-04 2014-08-23 2 I want to find the number of rows that were active at any time during each month. Ex. Jan: 4 Feb: 2 Mar: 1 etc... I figured out how to do this for a single month, but I'm struggling with how to do it for all 12 months in a year in a single query. The reason I would like it in a single query is for performance, as information is used immediately and caching wouldn't make sense in this scenario. Here's the code I have for a month at a time. It checks if the activate date comes before the end of the month in question and that the deactivate date was not before the beginning of the period in question. SELECT * from tblName WHERE activate <= DATE_SUB(NOW(), INTERVAL 1 MONTH) AND deactivate >= DATE_SUB(NOW(), INTERVAL 2 MONTH) If anybody has any idea how to change this and do grouping such that I can do this for an indefinite number of months I'd appreciate it. I'm at a loss as to how to group.
If you have a table of months that you care about, you can do:
select m.*,
(select count(*)
from table t
where t.activate_date <= m.month_end and
t.deactivate_date >= m.month_start
) as Actives
from months m;
If you don't have such a table handy, you can create one on the fly:
select m.*,
(select count(*)
from table t
where t.activate_date <= m.month_end and
t.deactivate_date >= m.month_start
) as Actives
from (select date('2015-01-01') as month_start, date('2015-01-31') as month_end union all
select date('2015-02-01') as month_start, date('2015-02-28') as month_end union all
select date('2015-03-01') as month_start, date('2015-03-31') as month_end union all
select date('2015-04-01') as month_start, date('2015-04-30') as month_end
) m;
EDIT:
A potentially faster way is to calculate a cumulative sum of activations and deactivations and then take the maximum per month:
select year(date), month(date), max(cumes)
from (select d, (#s := #s + inc) as cumes
from (select activate_date as d, 1 as inc from table t union all
select deactivate_date, -1 as inc from table t
) t cross join
(select #s := 0) param
order by d
) s
group by year(date), month(date);