my demand is:from database query newest data,according to time field as a standard,query alarmtime this field ,but alarmtime < time
executive sql:
SELECT
c.entryTime AS alarmtime ,
a.time AS time
FROM (
SELECT
t.DB33,
MAX( t.Time ) AS time,
t.Stream,
t.Coil,
t.`View`
FROM (
SELECT DB33, Time, Stream, Coil, `View`
FROM running_check
ORDER BY id DESC
LIMIT 1000 ) as t
GROUP BY t.DB33 ) AS a
LEFT JOIN (
select cameraID,cameraName
from monitor_link_info) as b ON a.db33 = b.cameraID
LEFT JOIN (
SELECT entryTime, cameraID
FROM result_video_v2
ORDER BY id DESC
limit 1000 ) AS c ON a.db33 = c.cameraId
GROUP BY a.db33, b.cameraName
ORDER BY a.time DESC, alarmtime DESC
execute result is unamiable,please look at image
now time column not what i want,Because he didn't change.
SELECT
c.entryTime AS alarmtime ,
a.time AS TIME
FROM
(
SELECT DB33, MAX(TIME) TIME, Stream, Coil, `View`
FROM running_check
ORDER BY id DESC
GROUP BY t.DB33
LIMIT 1000
) AS a
LEFT JOIN
(
SELECT cameraID,cameraName
FROM monitor_link_info
GROUP BY cameraID
LIMIT 1000
) AS b ON (a.db33 = b.cameraID)
LEFT JOIN (
SELECT entryTime, cameraID
FROM result_video_v2
GROUP BY cameraID
ORDER BY id DESC
LIMIT 1000
) AS c ON (a.db33 = c.cameraID)
GROUP BY a.db33, b.cameraName
ORDER BY a.time DESC, c.entryTime DESC
Related
I have a History table that represents messages that are stored by some sort of chat program.
It has a user id, message & datetime. (specified on: http://sqlfiddle.com/#!9/49fcefb/5)
Now, what I want is to have a result which contains:
The max amount of messages typed by date
What user has the most messages and howmany messages this user typed)
I got it working, but I find the query rather slow, I think its because of the last GROUP BY (GROUP BY b.cnt) as this will group over all the records found.
Query:
SELECT b.cnt as dayCount, a.cnt as userCount, a.userid as userId, b.date
FROM (
select date_added as date, user_id as userid, count(*) as cnt from history group by userid, day(date_added),month(date_added),year(date_added)
) a
INNER JOIN (
select date_added as date, count(*) as cnt from history group by day(date_added),month(date_added),year(date_added)
) b ON year(a.date) = year(b.date)
AND month(a.date) = month(b.date)
AND day(a.date) = day(b.date)
GROUP BY b.cnt
ORDER BY dayCount desc, userCount desc limit 10;
Can someone advice me on how to solve this? Maybe with another sort of query?
Thanks in advance!
You can try using windows function with Subquery to get the same result.
select SQ.daycount,SQ.usercount,SQ.user_id, SQ.date1 from (
select sum(count(Message)) over (partition by date(date_added)) as daycount, --to get max amount of msg by date
max(count(Message)) over (partition by date(date_added)) as maxuser, -- to identify user with most msg
count(Message) as usercount,
date(date_added) as date1,user_id from history
group by date1,user_id ) SQ
where SQ.usercount=SQ.maxuser
Check the Fiddle here
seems you are joining with wrong criteria.
first table is getting the # of users, 2nd table is getting the #of days per user_id. see dbfiddle
SELECT b.cnt as dayCount, a.cnt as userCount, a.userid as userId, b.date
FROM (
select
user_id as userid
, count(*) as cnt
from history
group by userid
) a
LEFT JOIN (
select cast(date_added as date) as date
, count(*) as cnt
, user_id as userid
from history
group by cast(date_added as date)
) b ON a.userid = b.userid
ORDER BY dayCount desc, userCount desc limit 10;
Is it possible to convert this subquery to join?
SELECT `news`.`newsId`,
(SELECT `comments`.`text`
FROM `comments`
WHERE `comments`.`newsId` = `news`.`newsId`
order by `comments`.`date` desc
limit 1)
FROM `news` , `comments`
where `news`.`newsId` = `comments`.`newsId`
GROUP BY `news`.`newsId`
order by news.date desc;
I assume newsId is unique.
SELECT `news`.`newsId`,
`comments`.`text`
FROM `news`
CROSS APPLY (SELECT `comments`.`text`
FROM `comments`
WHERE `comments`.`newsId` = `news`.`newsId`
order by `comments`.`date` desc
limit 1) cm
order by news.date desc;
I think that what you're trying to do is:
SELECT n.newsId FROM news n
INNER JOIN comments c ON c.newsId = n.newsId
ORDER BY c.date DESC, n.date
LIMIT 1
The GROUP BY is not necessary as you are not using any aggregation function. You can have unique entries with DISTINCT
I have a calendar and user_result table and I need to join these two queries.
calendar query
SELECT `week`, `date`, `time`, COUNT(*) as count
FROM `calendar`
WHERE `week` = 1
GROUP BY `date`
ORDER BY `date` DESC
and the result is
{"week":"1","date":"2014-08-21","time":"15:30:00","count":"4"}, {"week":"1","date":"2014-08-20","time":"17:30:00","count":"12"}
user_result query
SELECT `date`, SUM(`point`) as score
FROM `user_result`
WHERE `user_id` = 1
AND `date` = '2014-08-20'
and the result is just score 3
My goal is to always show calendar even if the user isn't present in the user_result table, but if he is, SUM his points for that day where calendar.date = user_result.date. Result should be:
{"week":"1","date":"2014-08-21","time":"15:30:00","count":"4","score":"3"}, {"week":"1","date":"2014-08-20","time":"17:30:00","count":"12","score":"0"}
I have tried this query below, but the result is just one row and unexpected count
SELECT c.`week`, c.`date`, c.`time`, COUNT(*) as count, SUM(p.`point`) as score
FROM `calendar` c
INNER JOIN `user_result` p ON c.`date` = p.`date`
WHERE c.`week` = 1
AND p.`user_id` = 1
GROUP BY c.`date`
ORDER BY c.`date` DESC
{"week":"1","date":"2014-08-20","time":"17:30:00","count":"4","score":"9"}
SQL Fiddle
ow sorry, i was edited, and i was try at your sqlfiddle, if you want to show all date from calendar you can use LEFT JOIN, but if you want to show just the same date between calendar and result you can use INNER JOIN, note: in this case INNER JOIN just show 1 result, and LEFT JOIN show 2 results
SELECT c.`week`, p.user_id, c.`date`, c.`time`, COUNT(*) as count, p.score
FROM `calendar` c
LEFT JOIN
(
SELECT `date`, SUM(`point`) score, user_id
FROM `result`
group by `date`
) p ON c.`date` = p.`date`
WHERE c.`week` = 1
GROUP BY c.`date`
ORDER BY c.`date` DESC
I put a pre-aggreate query / group by date as a select for the one person you were interested in... then did a left-join to it. Also, your column names of week, date and time (IMO) are poor choice column names as they can appear to be too close to reserved keywords in MySQL. They are not, but could be confusing..
SELECT
c.week,
c.date,
c.time,
coalesce( OnePerson.PointEntries, 0 ) as count,
coalesce( OnePerson.totPoints, 0 ) as score
FROM
calendar c
LEFT JOIN ( select
r.week,
r.date,
COUNT(*) as PointEntries,
SUM( r.point ) as totPoints
from
result r
where
r.week = 1
AND r.user_id = 1
group by
r.week,
r.date ) OnePerson
ON c.week = OnePerson.week
AND c.date = OnePerson.date
WHERE
c.week = 1
GROUP BY
c.date
ORDER BY
c.date DESC
Posted code to SQLFiddle
I'm trying to get a subset of records in a GROUP BY, I've seen a lot of crazy solutions out there, but they just seem too complicated, is there any more efficient way to do this.
SELECT user_id, GROUP_CONCAT(item_id ORDER BY `timestamp`) AS items
FROM wb_user_book_current_item GROUP BY user_id
So this will return me all the current items for all users which is okay so far. But I only want the ten most recent items. Adding ORDER BY to the GROUP_CONCAT helps, but it still doesn't give me the last ten records.
EDIT
If I do something like this and hard code the user_id then I can get the results I want for that one user, problem is combining it so that I don't need to hard code the user_id and can for instance just get ALL users last ten items
SELECT GROUP_CONCAT(cp2.item_id) AS items
FROM (SELECT cp.user_id, cp.item_id
FROM wb_user_book_current_item cp
WHERE cp.user_id=1 ORDER BY cp.`timestamp`
LIMIT 10) AS cp2
GROUP BY cp2.user_id
This is a difficult problem, but how about this:
SELECT user_id, GROUP_CONCAT(item_id ORDER BY `timestamp`) AS items
FROM wb_user_book_current_item T
WHERE NOT EXISTS
(
SELECT 1
FROM wb_user_book_current_item T2
WHERE T2.user_id = T.user_id
ORDER BY T2.`timestamp` DESC
LIMIT 10,1
)
OR T.`timestamp` > (
SELECT T2.`timestamp`
FROM wb_user_book_current_item T2
WHERE T2.user_id = T.user_id
ORDER BY T2.`timestamp` DESC
LIMIT 10,1
)
GROUP BY user_id
This of course assumes you won't have two rows with the same timestamp for the same user.
If your timestamp field is always a positive integer, you can also replace the NOT EXISTS...OR with a COALESCE:
SELECT user_id, GROUP_CONCAT(item_id ORDER BY `timestamp`) AS items
FROM wb_user_book_current_item T
WHERE T.`timestamp` > COALESCE((
SELECT T2.`timestamp`
FROM wb_user_book_current_item T2
WHERE T2.user_id = T.user_id
ORDER BY T2.`timestamp` DESC
LIMIT 10,1
), 0)
GROUP BY user_id
Original answer, but apparently MySQL doesn't understand how to do this properly and complains the subselect returns multiple rows. Of course we want multiple rows; it's a GROUP_CONCAT. Grr.
Unfortunately, I think there's no real way around using a subquery:
SELECT T.user_id,
GROUP_CONCAT((SELECT T2.item_id
FROM wb_user_book_current_item T2
WHERE T2.user_id = T.user_id
ORDER BY T2.`timestamp`
LIMIT 10)) AS items
FROM wb_user_book_current_item T
GROUP BY user_id
Otherwise, adding LIMIT anywhere else will either limit the number of groups, or limit from the total recordset over the table (and not the group) - neither of which are what you are trying to achieve.
So came across a nice solution here that works pretty well.
http://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/
It's something like this put all together:
SET #num := 0, #user_id := '';
SELECT cp2.user_id, CONCAT(cp2.item_id) AS items
FROM (
SELECT cp.user_id, cp.item_id,
#num := IF(#user_id = cp.user_id, #num + 1, 1) AS row_number,
#user_id := cp.user_id AS dummy
FROM wb_user_curent_item AS cp
ORDER BY cp.user_id ASC, cp.`timestamp` DESC
) AS cp2 WHERE cp2.row_number <= 10
GROUP BY cp2.user_id
So basically it just uses the num increment to limit the records rather than using LIMIT
SELECT
i.user_id,
GROUP_CONCAT(i.item_id ORDER BY i.timestamp) AS items
FROM
( SELECT DISTINCT user_id
FROM wb_user_book_current_item
) AS du
JOIN
wb_user_book_current_item AS i
ON i.user_id = du.user_id
AND i.timestamp <= COALESCE(
( SELECT i2.item_id
FROM wb_user_book_current_item AS i2
WHERE i2.user_id = du.user_id
ORDER BY i2.timestamp ASC
LIMIT 1 OFFSET 9
)
, '2038-01-19 03:14:07')
GROUP BY
i.user_id ;
An index on (user_id, timestamp, item_id) will help efficiency.
Try this:
SELECT
user_id,
GROUP_CONCAT(item_id ORDER BY `timestamp`) AS items
FROM wb_user_book_current_item
GROUP BY user_id
LIMIT 0, 10
UPDATE: I didn't notice the GROUP_CONCAT so you will have to use sub query in conunction with LIMIT
use LIMIT
SELECT column_name(s)
FROM table_name
LIMIT number
I have a MySQL query like this:
SELECT *
FROM backstage
WHERE backstage_id IN (
SELECT backstage_id
FROM visitor_counter
WHERE backstage_id !=0
GROUP BY backstage_id
ORDER BY COUNT( DISTINCT ( ip_address ) ) DESC
)
LIMIT 0 , 100
I get the results I want, but I would like to order it by COUNT( DISTINCT ( ip_address ) ) DESC as the inner question does.
Any tips on how to do this?
Give this a go and see if it gives you what you're after:
select bs.*
from backstage bs
inner join
(
select backstage_id,count(distinct ip_address) as distIpCount
from visitor_counter
where backstage_id !=0
group by backstage_id
) vc on vc.backstage_id = bs.backstage_id
order by vc.distIpCount desc
limit 0,100;