I have a mysql table with a column "timestamp".
Now I want to select the elements with a difference of 5 minutes from each other.
Simplified example:
id | timestamp
===================
1 | 00:00
2 | 00:01
3 | 00:03
4 | 00:05
5 | 00:07
6 | 00:09
7 | 00:15
should return the ids 1, 4, 7
is this possible with a sql statement?
Here's a solution, which should work no matter what's the first timestamp.
SELECT id, ts FROM (
SELECT
IF(UNIX_TIMESTAMP(ts) = #prev OR UNIX_TIMESTAMP(ts) % 300 = #prev % 300, #mybool:=1, #mybool:=0) AS mybool,
IF(#mybool = 1, #prev:=UNIX_TIMESTAMP(ts), #prev:=#prev),
t.*
FROM Table2 t,
(SELECT #prev:=(SELECT MIN(UNIX_TIMESTAMP(ts)) FROM Table2 sqt), #mybool:=1) vars
ORDER BY id
) sq
WHERE mybool = 1;
See it working live in an sqlfiddle.
If the first timestamp is '00:00' you can simply do
SELECT *
FROM Table1
WHERE UNIX_TIMESTAMP(ts) % 300 = 0
ORDER BY id;
but you have to work with UNIX_TIMESTAMP() to make it work. A timestamp is stored in database as a 32-bit integer, still you have to tell MySQL that you want to work with the integer representation.
select id from table where timestamp % 5 = 0
Precise syntax depends a bit on the datatype of the timestamp column but in general you should be able to do it with the modulo operator.
Related
I have two tables, both with a Time column as timestamp type which is filled by default when the row is created: Table1 is updated approximately every 10 seconds:
Time | Val_1a | Val_2a | Val_3a
2021-11-06 13:59:53 | 15 | 10 | 35
2021-11-06 14:00:02 | 12 | 15 | 34
.................
2021-11-06 14:05:25 | 11 | 13 | 35
2021-11-06 14:05:35 | 11 | 17 | 36
Table2 is updated every hour after mathematical operations on table1:
Time | Var_1b | Var_2b | Var_3b
2021-11-06 11:00:00 | 2 | 15 | 30
2021-11-06 12:00:00 | 8 | 12 | 32
2021-11-06 13:00:00 | 12 | 11 | 35
What I would like to get but I'm not able to do in any way, is:
Check that the last table1.Val_2a value is greater than the first table1.Val_2a value written at the beginning of the current hour (with the tables above, check if 17 > 15). If this condition is not met, the entire query must return 0 otherwise:
2a) If the last row in table2 refers to the previous day, then the query result is simply the difference of the two table1.Val_2a values (17 - 15 = 2)
2b) Otherwise their difference is calculated as at point 2a (17-15 = 2) and it is added to the table2.Var_1b value (2 + 12 = 14)
I hope I was able to explain it in a clearly way, and that it all is possible with a single query. Thanks everyone for the support
Sorry, if I add an Answer but I couldn't add the image into the comment.
This is the qwery I used to test the CASE clause
SELECT t1.dtm, t1.Val_2a2, t1.Val_2a1,
CASE WHEN Val_2a2 > Val_2a1
THEN Val_2a2-Val_2a1 ELSE 0 END AS ValF FROM (SELECT DATE_FORMAT(time, '%Y-%m-%d %H:00:00') dtm,
SUBSTRING_INDEX(GROUP_CONCAT(Val_2a ORDER BY time),',',1) Val_2a1,
SUBSTRING_INDEX(GROUP_CONCAT(Val_2a ORDER BY time DESC),',',1) Val_2a2 FROM table1 GROUP BY dtm) t1
and this is the unexpected result
Qwery result
It is possible in a single query but different people will have different method of doing it. Whatever the method is, I personally think that the most important part is to keep the logic intact. The details you've provided in your question got me assuming that this might be a kind of query you're looking for:
SELECT t1.dtm, t1.Val_2a2, t1.Val_2a1, t2.Val_1b2,
CASE WHEN Val_2a2 > Val_2a1
THEN Val_2a2-Val_2a1+Val_1b2 ELSE 0 END AS ValF
FROM
(SELECT DATE_FORMAT(time, '%Y-%m-%d %H:00:00') dtm,
SUBSTRING_INDEX(GROUP_CONCAT(Val_2a ORDER BY time),',',1) Val_2a1 ,
SUBSTRING_INDEX(GROUP_CONCAT(Val_2a ORDER BY time DESC),',',1) Val_2a2
FROM table1
GROUP BY dtm) t1
LEFT JOIN
(SELECT DATE(time) dtm,
SUBSTRING_INDEX(GROUP_CONCAT(Val_1b ORDER BY time DESC),',',1) Val_1b2
FROM table2
GROUP BY dtm) t2
ON DATE(t1.dtm)=t2.dtm;
Demo fiddle
hoping it can help someone else, after some more test this is the final qwery I got, considering I just need a value on the fly without needing of storing it.
Of course every consideration by the experts is more than appreciate.
Thanks to all
SELECT
CASE WHEN
(ABS(t1.Val_2a2) - ABS(t1.Val_2a1)) BETWEEN 0 AND 30
THEN t1.Val_2a2-t1.Val_2a1+t2.Val_1b2
ELSE t2.Val_1b2
END AS My_result
FROM
(SELECT DATE_FORMAT(Time, '%Y-%m-%d %H:00:00') dtm,
(SELECT Val_2a FROM table1 WHERE Time >= DATE_FORMAT(NOW(),"%Y-%m-%d %H:00:00") ORDER BY Time LIMIT 1) Val_2a1,
(SELECT Val_2a FROM table1 WHERE Time >= DATE_FORMAT(NOW(),"%Y-%m-%d %H:00:00") ORDER BY Time DESC LIMIT 1) Val_2a2
FROM table1
GROUP BY dtm
ORDER BY Time DESC LIMIT 1) t1
LEFT JOIN
(SELECT (Time) dtm,
(Val_1b) Val_1b2
FROM table2
GROUP BY dtm ORDER BY dtm DESC LIMIT 1) t2
ON DATE(t1.dtm)= DATE(t2.dtm)
I am looking to write a query that shows all hours even when no data is present. I have seen some posts where the suggestion is to create a temporary table that has all the hours listed but I am not sure how to do that. Here is my current query:
select DATE_FORMAT(t_stamp, "%h %p") as Hour, count(*) as Count
from cyclehistory
where DATE(t_stamp) = CURRENT_DATE()
group by hour(t_stamp)
This works returns the following
Hour | Count
09 AM | 6
10 AM | 11
1 PM | 5
But I would like it to return
Hour | Count
.
.
.
09 AM | 6
10 AM | 11
11 AM | 0
12 PM | 0
1 PM | 5
.
.
You do need some kind of table of numbers to do this. Here, you just need 24 numbers, from 0 to 23. Say the numbers table is called numbers with column num:
select maketime(n.num, 0, 0) as t_time, count(c.t_stamp) cnt
from numbers n
left join cyclehistory c
on hour(c.tstamp) = n.num
and c.t_stamp >= current_date and c.t_stamp < current_date + interval 1 day
group by n.num
There are multiple ways to build the number table. You can create a table and insert records manually:
create table numbers (num int primary key);
insert into numbers values (0), (1), ..., (23);
For a one-time task, you can create a derived table directly in the query:
select ...
from (
select 0 num
union all select 1
...
union all select 23
) numbers
left join ...
In MySQL 8.0, you can use a recursive query:
with recursive numbers (num) as (
select 0
union all select num + 1 from cte where num < 23
)
select ...
from numbers
left join ...
I have a MySQL table with a datetime row. How can I find all groups with at least 5 entries within 10 minutes?
My only idea is to write a program (in whatever language) and loop over the timestamps, check always 5 (..) successive entries, calculate the time span between the last and the first and check whether it is below the limit.
Can this be done using a single SQL query too?
(The scenario is is simplified and the numbers are just examples.)
As requested, here comes an example:
id | timestamp | other_column
---|---------------------|-------------
3 | 2017-01-01 11:00:00 | thank
2 | 2017-01-01 11:01:00 | you
1 | 2017-01-01 11:02:00 | for
* 6 | 2017-01-01 11:20:00 | your
* 5 | 2017-01-01 11:21:00 | efforts
* 4 | 2017-01-01 11:22:00 | to
* 7 | 2017-01-01 11:23:00 | help
* 8 | 2017-01-01 11:24:00 | me
9 | 2017-01-01 11:40:00 | :
10 | 2017-01-01 11:41:00 | )
If the count limit is 5 and the timespan limit is 10 minutes, I'd like to get the entries marked with "*". The "id" column is the primary key of the table, but the order is not always the order of the timestamps. The "other_column" is used for a where clause. The table has about 1 million entries.
Try to break this down logically. Sorry for the psuedo code bits, I'm a little short on time.
select t1.id, t1.timestamp, t2.timestamp
from yourtable t1
inner join yourtable t2 on t2.timestamp >= t1.timestamp and t2.timestamp < (t1.timestamp + 20 minutes)
(plus 20 minutes won't work as is, use appropriate add function)
So this will give you a relatively giant list of all ID's joined to any other id's within a 20 minute time interval (including one row for itself). (add, I'm only picking out the first row of the group at this point, easier just to grab the 'header row' here by this timestamp plus 20 minutes and worry about the rest in the next step) If we group by the ID and time, we get a count of how many rows were within 20 minutes:
select id, t1.timestamp, count(1)
from yourtable t1
inner join yourtable t2 on t2.timestamp >= t1.timestamp and t2.timestamp < (t1.timestamp + 20 minutes)
group by id, t1.timestamp
having count(1) > 4
This will now give you a list of all the ID's and it's timestamp that has itself and 4 other records or more within 20 minutes away from that timestamp. Now it depends on how you want to group from here, if you want each of the 5 lines, we can call the query above a subquery and join it back to the main table to get the rows you want returned.
select t3.*
from
(select id, t1.timestamp, count(1)
from yourtable t1
inner join yourtable t2
on t2.timestamp >= t1.timestamp and t2.timestamp < (t1.timestamp + 20 minutes)
group by id, t1.timestamp
having count(1) > 4) a
inner join yourtable t3 on t3.timestamp >= a.timestamp and t3.timestamp < (a.timestamp + 20 minutes)
And that should give you ID 4-8 and it's info returned (order as you see fit).
My apologies that I don't have the time to test, but the logic should work.
I have a table in my database that contains an ID and DATETIME column, here is some sample data:
ID | DATETIME
1 | 2014-05-06 01:12
1 | 2014-05-06 01:30
1 | 2014-05-06 01:45
1 | 2014-05-06 02:59
2 | 2014-05-06 01:17
2 | 2014-05-06 01:18
2 | 2014-05-06 01:19
2 | 2014-05-06 02:00
I need to produce a query that determines the ID belonging to the object that has the longest time between its DATETIME values, where the time between consecutive DATETIME values does not exceed 20 minutes.
For example, in the sample data, I would want to return 1 as it has DATETIME values from (01:12 - 01:45) without having a consecutive difference of 20 minutes between DATETIME values.
Thanks.
It looks like you will need a self-join. Because if you had 10 entries for an ID, your 20 minute gap might be between entries 3-6 vs 1-4 or even 4-9. So the second instance of the join would be on the same ID and have a date time higher than that of the primary entry, but less than 20 minutes. Then, it could be ordered by the time-gap and limit to the one you want. Something like:
select
YT.ID,
YT.DTColumn,
MAX( YT2.DTColumn ) as MaxDateWithin20Minutes
from
YourTable YT
JOIN YourTable YT2
ON YT.ID = YT2.ID
AND YT.DTColumn < YT2.DTColumn
AND YT2.DTColumn <= date_add( YT.DTColumn, INTERVAL 20 MINUTE )
group by
YT.ID,
YT.DTColumn
order by
timediff(MAX( YT2.DTColumn ), YT.DTColumn) DESC
limit
1
You need to get the next (or previous) value and get the time difference. I think the following does what you want:
select t.*
from (select t.*,
(select t2.datetime
from table t2
where t2.id = t.id and t2.datetime < t.datetime
order by t2.datetime desc
) prev_datetime
from table t
) t
where datetime <= prev_datetime + interval 20 minutes
order by timestampdiff(second, prev_datetime, datetime) desc
limit 1;
I am trying to generate a table in the following format.
Proday | 2014-04-01 | 2014-03-01
--------------------------------
1 | 12 | 17
2 | 6 | 0
7 | 0 | 24
13 | 3 | 7
Prodays (duration between two timestamps) is a calculated value and the data for months is a COUNT. I can output the data for a single month, but am having troubles joining queries to additional months. The index (prodays) may not match for each month. e.g.. 2014-04-01 may not have any data for Prodays 7, whereas 2014-03-01 may not have Proday 2. Should indicate with 0 or null.
I suspect FULL OUTER JOIN is what should do the trick. But have read that's not possible in Mysql?
This is the query to get data for a single month:
SELECT round((protime - createtime) / 86400) AS prodays, COUNT(id) AS '2014-04-01'
FROM `tbl_users` as t1
WHERE status = 1 AND DATE_FORMAT(FROM_UNIXTIME(createtime),'%Y-%m-%d') >= '2014-04-01'
AND DATE_FORMAT(FROM_UNIXTIME(createtime),'%Y-%m-%d') <= LAST_DAY('2014-04-01')
GROUP BY prodays
ORDER BY `prodays` ASC
How can I join/union an additional query to create a column for 2014-03-01?
You want to use conditional aggregation -- that is, move the filtering logic from the where clause to the select clause:
SELECT round((protime - createtime) / 86400) AS prodays,
sum(DATE_FORMAT(FROM_UNIXTIME(createtime),'%Y-%m-%d') >= '2014-04-01' AND
DATE_FORMAT(FROM_UNIXTIME(createtime),'%Y-%m-%d') <= LAST_DAY('2014-04-01')
) as `2014-04-01`,
sum(DATE_FORMAT(FROM_UNIXTIME(createtime),'%Y-%m-%d') >= '2014-03-01' AND
DATE_FORMAT(FROM_UNIXTIME(createtime),'%Y-%m-%d') <= LAST_DAY('2014-03-01')
) as `2014-03-01`
FROM `tbl_users` as t1
WHERE status = 1
GROUP BY prodays
ORDER BY `prodays` ASC;