I have a table in MySQL with some data of a temperature sensor. I have 1 row per minute. I would like to perform a query to know whether there was any span of 1 hour where the average temperature was greater than 4 degrees. I know how to perform a query where a single row was above 4:
SELECT * FROM sensor WHERE t>4
But in my case, I want to know whether there was a 1 hour period where the average temperature was over 4, not only a single row.
Not sure how to write such query...
One method is:
select s.*
from sensor s
where t > 4 and
not exists (select 1
from sensor s2
where s2.datetime >= s.datetime and
s2.datetime < s.datetime + interval 1 hour and
s2.t <= 4
);
EDIT:
Arggh. The question asks about the average temperature, not any temperature (the question is quite clear, I just misread it).
Here is a variation to handle that:
select s.*,
(select avg(s2.t)
from sensor s2
where s2.datetime >= s.datetime and
s2.datetime < s.datetime + interval 1 hour
) as avg_t
from t
having avg_t > 4;
This uses an extension to MySQL where the having clause can make use of a column alias for filtering.
SELECT DATE_FORMAT(DATE_TIME_FIELD, '%Y-%m-%d %H') AS DATE_TIME_HOUR
FROM sensor
GROUP BY DATE_FORMAT(DATE_TIME_FIELD, '%Y-%m-%d %H')
HAVING AVG(T)>4
Another method is:
SELECT *,
AVG(`t`) AS `avg_t`,
DATE_FORMAT(`date`, '%Y-%m-%d %H') AS `date_and_hour`
FROM `sensor`
GROUP BY DATE_FORMAT(`date`, '%Y-%m-%d %H')
HAVING `avg_t` > 4;
Related
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;
RDBMS: MySQL
The time column(s) datatype is of datetime
For every hour of the 24 hour day I need to retrieve the number of rows in which their start_time matches the hour OR the end_time is great than or equal to the hour.
Below is the current query I have which returns the data I need but only based off of one hour. I can loop through and do 24 separate queries for each hour of the day but I would love to have this in one query.
SELECT COUNT(*) as total_online
FROM broadcasts
WHERE DATE(start_time) = '2018-01-01' AND (HOUR(start_time) = '0' OR
HOUR(end_time) >= '0')
Is there a better way of querying the data I need? Perhaps by using group by somehow? Thank you.
Not exactly sure if i am following, but try something like this:
select datepart(hh, getdate()) , count(*)
from broadcasts
where datepart(hh, starttime) <=datepart(hh, endtime)
and cast(starttime as date)=cast(getdate() as date) and cast(endtime as date)=cast(getdate() as date)
group by datepart(hh, getdate())
Join with a subquery that returns all the hour numbers:
SELECT h.hour_num, COUNT(*) AS total_online
FROM (SELECT 0 AS hour_num UNION SELECT 1 UNION SELECT 2 ... UNION SELECT 23) AS h
JOIN broadcasts AS b ON HOUR(b.start_time) = h.hour_num OR HOUR(b.end_time) >= h.hour_num
WHERE DATE(b.start_time) = '2018-01-01'
GROUP BY h.hour_num
I am using MySQL. Here is my schema:
bannerstatclick(idBannerStats: integer, Time: Timestamp, idCampaignBanner :char(36))
I am trying to write a query to select the total no of click month wise by using count on idCampaignBanner.
this will not work it will give an error invalid use of group function.
iwill also try this using having clause but it also not work...
SELECT count(idCampaignBanner) AS TotalClicks ,max(`Time`) AS maxdate,(min(`Time`) + INTERVAL 30 DAY)as monthly
FROM newradium.BannerStatsClick
WHERE Time BETWEEN max(`Time`) AND ( max(`Time`)- INTERVAL 30 DAY)
Something like this should work (you need group by clause if you do aggregation)
select count(idCampaignBanner), MONTH(`Time`) as m
from newradium.BannerStatsClick
group by m
SELECT
count(idCampaignBanner) AS TotalClicks
, max(`Time`) AS maxdate
, (min(`Time`) + INTERVAL 30 DAY)as monthly
FROM newradium.BannerStatsClick
WHERE Time <= (Select max(`Time`) FROM newradium.BannerStatsClick)
And Time >= (Select max(`Time`) - INTERVAL 30 DAY FROM newradium.BannerStatsClick)
Technically could get rid of "Time <= (Select max(Time) FROM newradium.BannerStatsClick)", doesn't really affect the selection. But left in in case you needed different range in future
I am trying to count time stamps between two databases but one has overlapping time stamps, due to not my design flaw.
SELECT date(time + INTERVAL 8 HOUR) as day, COUNT(DISTINCT comment)
FROM news.data
GROUP BY day
UNION ALL
SELECT date(time + INTERVAL 8 HOUR) as day, COUNT(DISTINCT comment)
FROM`news-backup`.`data`
GROUP BY day
ORDER BY year(day) desc, day(day) DESC
LIMIT 20
What seems to happen, there are some timestamps in range of both databases so they produce separate counts for certain dates. So it would give count for TODAY from news and news-backup
EX:
date count
2013-1-15 10
2013-1-15 13
2013-1-14 8
2013-1-13 15
What I want is
EX:
date count
2013-1-15 23
2013-1-14 8
2013-1-13 15
Here is a kicker, I need it in a view, so there are some limitations with that (no subqueries allowed). Thoughts? And no I cannot change the data dump sequence that happens between to DBs
You can't put a subquery in a view, but you can put a view in a view.
So:
create view1 as
SELECT date(time + INTERVAL 8 HOUR) as day, 'current' as which, COUNT(DISTINCT comment) as cnt
FROM news.data
GROUP BY day
UNION ALL
SELECT date(time + INTERVAL 8 HOUR) as day, 'backup' as which, COUNT(DISTINCT comment) as cnt
FROM`news-backup`.`data`
GROUP BY day, which
I'm not sure what you logic for combining them is:
create view2 as
select day, max(cnt) -- sum(cnt)? prefer current or backup?
from view1
group by day
ORDER BY day desc
The documentation that bans subqueries is here. Be sure to search for "The SELECT statement cannot contain".
If you have a table of all the dates, the following "absurd" SQL might work:
select c.date,
coalesce( (select count(distinct comment) from news.data where date(time + INTERVAL 8 HOUR) = c.date),
(select count(distinct comment) from news_backup.data where date(time + INTERVAL 8 HOUR) = c.date)
) as NumComments
from calendar c
This version is assuming you want the "new" first, then the backup. If you want the sum, then you would add them.
I want to get the value of users visiting my page for 10 days in a chart. I need to COUNT() all the values from the last ten days.
The best layout would be
Day|COUNT(ip)
1 - 10
2 - 12
3 - 52
......
I hope you understand what I mean.
Can MySQL do this directly or need I to do this in PHP in 10 seperate querys?
Regards,
Moritz
Update with Tablestructure:
Id (Auto Increment)|Time (Unix Timestamp)|Ip|Referer
This should run fast for you
SELECT COUNT(ip) ipcount,dt FROM
(
SELECT ip,DATE(FROM_UNIXTIME(`Time`)) as dt FROM mytable
WHERE `Time` > TO_UNIXTIME(NOW() - INTERVAL 10 DAY)
) A GROUP BY dt;
Make sure you have an index on Time
ALTER TABLE mytable ADD INDEX TimeIndex (`Time`);
This will give you results with actual date values:
SELECT
COUNT(DISTINCT ip),
FROM_UNIXTIME(Time, '%m/%d/%Y') AS Day
FROM
tbl
WHERE
Time >= UNIX_TIMESTAMP(DATE_ADD(CURDATE(), INTERVAL -10 DAY))
GROUP BY
FROM_UNIXTIME(Time, '%m/%d/%Y')
try this:
SELECT CAST(DATE(FROM_UNIXTIME(`Time`)) AS CHAR) as dateoftime, COUNT(Ip) as cnt
FROM tablename
WHERE DATE(FROM_UNIXTIME(`Time`)) > DATE_SUB(current_timestamp, INTERVAL 10 DAY)
GROUP BY CAST(DATE(FROM_UNIXTIME(`Time`)) AS CHAR)