I have a table with three columns (user, timestamp, activity). The activity is basically check in or check out. How do I generate a query to view total seconds a user has clocked in by day?
There is an issue with the system that sometimes has two check ins but only one check out...in which case I want to only take the lowest check in timestamp.
I came up with something like this (activity: 1 = check in, 0 = checkout):
select a.user_id, a.d, time_to_sec(TIMEDIFF(b.created_at, a.created_at)) total_secs,
a.created_at check_in, b.created_at check_out
from (select user_id, created_at, date(created_at) d, #rownum := #rownum + 1 AS num from table, (SELECT #rownum := 0) r where activity = 1 order by user_id, created_at) a
join (select user_id, created_at, date(created_at) d, #rownum2 := #rownum2 + 1 AS num from table, (SELECT #rownum2 := 0) r where activity = 0 order by user_id, created_at) b
on a.user_id = b.user_id and a.d = b.d and a.num = b.num
However, I think relying on rownum is not accruate
If I understand your requirement correctly, you want the number of seconds between a checkout and the earliest check-in before that, but after the previous checkout.
So what you would need is a query that joins a checkout with the previous checkout and then with the earliest check-in between these two activities.
select
curr_co.user_id,
curr_co.created_at,
max(prev_co.created_at)
from
table as curr_co
left outer join
table as prev_co
on (curr_co.user_id = prev_co.user_id and curr_co.created_at > prev_co.created_at and curr_co.activity = _checkout_ and prev_co.activity = _checkout_)
group by curr_co.user_id, curr_co.created_at
This query should give you a list of checkouts with previous checkouts per user.
Now select all check-ins in between and from those the minimal and calculate the diff.
select ... min(ci.created_at), time_to_sec(TIMEDIFF(min(ci.created_at), curr_co.created_at))
... join
table as ci
on (ci.user_id = curr_co.user_id and ci.created_at < curr_co.created_at and ci.created_at > prev_co.created_at and ci.activity = _check-in_)
Related
I have the following structure in my user table:
id(INT) registered(DATETIME)
1 2016-04-01 23:23:01
2 2016-04-02 03:23:02
3 2016-04-02 05:23:03
4 2016-04-03 04:04:04
I want to get the total (accumulated) user count per day, for all days in DB
So result should be something like
day total
2016-04-01 1
2016-04-02 3
2016-04-03 4
I tried some sub querying, but somehow i have now idea how to achieve this with possibly 1 SQL statement. Of course if could group by per day count and add them programmatically, but i don't want to do that if possible.
You can use a GROUP BY that does all the counts, without the need of doing anything programmatically, please have a look at this query:
select
d.dt,
count(*) as total
from
(select distinct date(registered) dt from table1) d inner join
table1 r on d.dt>=date(r.registered)
group by
d.dt
order by
d.dt
the first subquery returns all distinct dates, then we can join all dates with all previous registrations, and do the counts, all in one query.
An alternative join condition that can give some improvements in performance is:
on d.dt + interval 1 day > r.registered
Not sure why not just use GROUP BY, without it this thing will be more complicated, anyway, try this;)
select
date_format(main.registered, '%Y-%m-%d') as `day`,
main.total
from (
select
table1.*,
#cnt := #cnt + 1 as total
from table1
cross join (select #cnt := 0) t
) main
inner join (
select
a.*,
if(#param = date_format(registered, '%Y-%m-%d'), #rowno := #rowno + 1 ,#rowno := 1) as rowno,
#param := date_format(registered, '%Y-%m-%d')
from (select * from table1 order by registered desc) a
cross join (select #param := null, #rowno := 0) tmp
having rowno = 1
) sub on main.id = sub.id
SQLFiddle DEMO
I want to the latest results for my patients. The following sql returns 69,000 results after 87 seconds in mysqlworkbench. I have made both 'date' and 'patientid' columns as index.
select Max(date) as MaxDate, PatientID
from assessment
group by PatientID
I think my table has approximately 440,000 in total. Is it because that my table is 'large'?
Is there a way to increase the speed of this query, because I will have to embed this query inside other queries. For example like below:
select aa.patientID, assessment.Date, assessment.result
from assessemnt
inner join
(select Max(date) as MaxDate, PatientID
from assessment
group by PatientID) as aa
on aa.patientID = assessment.patientID and aa.MaxDate = assessment.Date
The above will give me the latest assessment results for each patient. Then I will also embed this piece of code to do other stuff... So I really need to speed up things. Anyone can help?
I wonder if this version would have better performance with the right indexes:
select a.patientID, a.Date, a.result
from assessemnt a
where a.date = (select aa.date
from assessment aa
where aa.patientID = a.patientID
order by aa.date desc
limit 1
);
Then you want an index on assessment(patientID, date).
EDIT:
Another approach uses an index on assessment(patient_id, date, result):
select a.*
from (select a.patient_id, a.date, a.result,
(#rn := if(#p = a.patient_id, #rn + 1,
if(#p := a.patient_id, 1, 1)
)
) as rn
from assessment a cross join
(select #p := -1, #rn := 0) params
order by patient_id desc, date desc
) a
where rn = 1;
So I have an event log that logs every 5 minutes so my logs look something like this:
OK
Event1
Event1
Event1
OK
Event1
OK
Event1
Event1
Event1
OK
In this case I'd have 3 instances of "Event1", since it had an "OK" period in between the periods when that status was returned.
Is there some decent way to handle this via mySql? (Note, there are other statuses other than Event1 / OK that come up quite regularly)
The actual Sql structure looks something like this:
-Historical
--CID //Unique Identifier, INT, AI
--ID //Unique Identifier for LOCATION, INT
--LOCATION //Unique Identifier for Location, this is the site name, VarChar
--STATUS //Pulled from Software event logger, VarChar
--TIME //Pulled from Software event logger, DateTime
Another answer using a totally different way of doing it:-
SELECT MAX(#Counter) AS EventCount -- Get the max counter
FROM (SELECT #Counter:=#Counter + IF(status = 'OK' AND #PrevStatus = 1, 1, 0), -- If it is an OK record and the prev status was not an OK then add 1 to the counter
#PrevStatus:=CASE
WHEN status = 'OK' THEN #PrevStatus := 2 -- An OK status so save as a prev status of 2
WHEN status != 'OK' AND #PrevStatus != 0 THEN #PrevStatus := 1 -- A non OK status but when there has been a previous OK status
ELSE #PrevStatus:=0 -- Set the prev status to 0, ie, for a record where there is no previous OK status
END
FROM (SELECT * FROM historical ORDER BY TimeStamp) a
CROSS JOIN (SELECT #Counter:=0, #PrevStatus := 0) b -- Initialise counter and store of prev status.
)c
This is using user variables. It has a subselect to get the records back in the right order, then uses a user variable to store a code for the previous status. Starts at 0 and when it finds a status of OK it sets the previous status to a 2. If it finds a status other than OK then it sets the prev status to 1, but ONLY if the prev status is not 0 (ie, it has already found a status of OK). Before storing the prev status code, if the current status is OK and the prev status code is a 1 then it adds 1 to the counter, otherwise it adds 0 (ie, adds nothing)
Then it just has a select around the outside to select the max value of the counter.
Seems to work but hardly readable!
EDIT - To cope with multiple ids
SELECT id, MAX(aCounter) AS EventCount -- Get the max counter for each id
FROM (SELECT id,
#PrevStatus:= IF(#Previd = id, #PrevStatus, 0), -- If the id has changed then set the store of previous status to 0
status,
#Counter:=IF(#Previd = id, #Counter + IF(status = 'OK' AND #PrevStatus = 1, 1, 0), 0) AS aCounter, -- If it is an OK record and the prev status was not an OK and was for the same id then add 1 to the counter
#PrevStatus:=CASE
WHEN status = 'OK' THEN #PrevStatus := 2 -- An OK status so save as a prev status of 2
WHEN status != 'OK' AND #PrevStatus != 0 THEN #PrevStatus := 1 -- A non OK status but when there has been a previous OK status
ELSE #PrevStatus:=0 -- Set the prev status to 0, ie, for a record where there is no previous OK status
END,
#Previd := id
FROM (SELECT * FROM historical ORDER BY id, TimeStamp) a
CROSS JOIN (SELECT #Counter:=0, #PrevStatus := 0, #Previd := 0) b
)c
GROUP BY id -- Group by clause to allow the selection of the max counter per id
Which is even less readable!
Another option, again using user variables to generate a sequence number:-
SELECT Sub1.id, COUNT(DISTINCT Sub1.aCounter) -- Count the number of distinct Sub1 records found for an id (without the distinct counter it would count all the recods between OK status records)
FROM (
SELECT id,
`TimeStamp`,
#Counter1:=IF(#Previd1 = id, #Counter1 + 1, 0) AS aCounter, -- Counter for this status within id
#Previd1 := id -- Store the id, used to determine if the id has changed and so whether to start the counters at 0 again
FROM (SELECT * FROM historical WHERE status = 'OK' ORDER BY id, `TimeStamp`) a -- Just get the OK status records, in id / timestamp order
CROSS JOIN (SELECT #Counter1:=0, #Previd1 := 0) b -- Initialise the user variables.
) Sub1
INNER JOIN (SELECT id,
`TimeStamp`,
#Counter2:=IF(#Previd2 = id, #Counter2 + 1, 0) AS aCounter,-- Counter for this status within id
#Previd2 := id-- Store the id, used to determine if the id has changed and so whether to start the counters at 0 again
FROM (SELECT * FROM historical WHERE status = 'OK' ORDER BY id, `TimeStamp`) a -- Just get the OK status records, in id / timestamp order
CROSS JOIN (SELECT #Counter2:=0, #Previd2 := 0) b -- Initialise the user variables.
) Sub2
ON Sub1.id = Sub2.id -- Join the 2 subselects based on the id
AND Sub1.aCounter + 1 = Sub2.aCounter -- and also the counter. So Sub1 is an OK status, while Sub2 the the next OK status for that id
INNER JOIN historical Sub3 -- Join back against historical
ON Sub1.id = Sub3.id -- on the matching id
AND Sub1.`TimeStamp` < Sub3.`TimeStamp` -- and where the timestamp is greater than the timestamp in the Sub1 OK record
AND Sub2.`TimeStamp` > Sub3.`TimeStamp` -- and where the timestamp is less than the timestamp in the Sub2 OK record
GROUP BY Sub1.id -- Group by the Sub1 id
This is grabbing the table twice for just the status OK records, adding a sequence number each time and matching where the id matches and the sequence number on the 2nd copy is 1 greater than the first one (ie, it is finding each OK and the OK immediately following it). Then joins that against the table where the id matches and the timestamp is between the 2 OK records. Then counts the distinct occurrences of the first counter for each id.
This should be a bit more readable.
Quick try, and I have a feeling I am missing a far better way to do this but think this will work.
SELECT COUNT(*)
FROM
(
SELECT DISTINCT a.time, b.time
FROM Historical a
INNER JOIN Historical b
ON a.time < b.time
AND a.status = 'OK'
AND b.status = 'OK'
INNER JOIN Historical c
ON a.time < c.time
AND c.time < b.time
AND c.status = 'Event1'
LEFT OUTER JOIN Historical d
ON a.time < d.time
AND d.time < b.time
AND d.status = 'OK'
WHERE d.cid IS NULL
) Sub1
Joins the table against itself repeatedly. Alias a and b should be for OK events, with c being for any Event1 event between those dates. Alias d is looking for an OK event between a and b, and if any are found then the record is dropped in the WHERE clause.
Then use DISTINCT to get rid of the duplicates. Then count the result.
Possible it could be simplified as something like the following (although probably best to cast the dates to chars in the select if doing this)
SELECT COUNT(DISTINCT CONCAT(a.time, b.time))
FROM Historical a
INNER JOIN Historical b
ON a.time < b.time
AND a.status = 'OK'
AND b.status = 'OK'
INNER JOIN Historical c
ON a.time < c.time
AND c.time < b.time
AND c.status = 'Event1'
LEFT OUTER JOIN Historical d
ON a.time < d.time
AND d.time < b.time
AND d.status = 'OK'
WHERE d.cid IS NULL
What you want to count, it seems, are instances of an event when the previous record is OK. You identify these with a correlated subquery, and then summarize to get the numbers:
select status, count(*)
from (select h.*,
(select h2.status
from historical h2
where h2.time < h.time
order by h2.time desc
limit 1
) as prevStatus
from historical h
) h
where status <> 'OK' and (prevStatus = 'OK' or prevStatus is NULL)
group by status;
It is not clear which column contains the values OK and Event1. I'm guessing it is status. I also don't know what role location plays, but this should at least get you started.
There is a table with the columns :
USE 'table';
insert into person values
('11','xxx','1976-05-10','p1'),
('11','xxx ','1976-06-11','p1'),
('11','xxx ','1976-07-21','p2'),
('11','xxx ','1976-08-31','p2'),
Can anyone suggest me a query to get the start and the end date of the person with respect to the place he changed chronologically.
The query I wrote
SELECT PId,Name,min(Start_Date) as sdt, max(Start_Date) as edt, place
from **
group by Place;
only gives me the first two rows of my answer. Can anyone suggest the query??
This isn't pretty, and performance might be horrible, but at least it works:
select min(sdt), edt, place
from (
select A.Start_Date sdt, max(B.Start_Date) edt, A.place
from person A
inner join person B on A.place = B.place
and A.Start_Date <= B.Start_Date
left join person C on A.place != C.place
and A.Start_Date < C.Start_Date
and C.Start_Date < B.Start_Date
where C.place is null
group by A.Start_Date, A.place
) X
group by edt, place
The idea is that A and B represent all pairs of rows. C will be any row in between these two which has a different place. So after the C.place is null restriction, we know that A and B belong to the same range, i.e. a group of rows for one place with no other place in between them in chronological order. From all these pairs, we want to identify those with maximal range, those which encompass all others. We do so using two nested group by queries. The inner one will choose the maximal end date for every possible start date, whereas the outer one will choose the minimal start date for every possible end date. The result are maximal ranges of chronologically subsequent rows describing the same place.
This can be achived by:
SELECT Id, PId,
MIN(Start_Date) AS sdt,
MAX(Start_Date) as edt,
IF(`place` <> #var_place_prev, (#var_rank:= #var_rank + 1), #var_rank) AS rank,
(#var_place_prev := `place`) AS `place`
FROM person, (SELECT #var_rank := 0, #var_place_prev := "") dummy
GROUP BY rank, Place;
Example: SQLFiddle
If you want records to be ordered by ID then:
SELECT Id, PId,
MIN(Start_Date) AS sdt,
MAX(Start_Date) as edt,
`place`
FROM(
SELECT Id, PId,
Start_Date
IF(`place` <> #var_place_prev,(#var_rank:= #var_rank + 1),#var_rank) AS rank,
(#var_place_prev := `place`) AS `place`
FROM person, (SELECT #var_rank := 0, #var_place_prev := "") dummy
ORDER BY ID ASC
) a
GROUP BY rank, Place;
I have a MySQL table with the structure:
beverages_log(id, users_id, beverages_id, timestamp)
I'm trying to compute the maximum streak of consecutive days during which a user (with id 1) logs a beverage (with id 1) at least 5 times each day. I'm pretty sure that this can be done using views as follows:
CREATE or REPLACE VIEW daycounts AS
SELECT count(*) AS n, DATE(timestamp) AS d FROM beverages_log
WHERE users_id = '1' AND beverages_id = 1 GROUP BY d;
CREATE or REPLACE VIEW t AS SELECT * FROM daycounts WHERE n >= 5;
SELECT MAX(streak) AS current FROM ( SELECT DATEDIFF(MIN(c.d), a.d)+1 AS streak
FROM t AS a LEFT JOIN t AS b ON a.d = ADDDATE(b.d,1)
LEFT JOIN t AS c ON a.d <= c.d
LEFT JOIN t AS d ON c.d = ADDDATE(d.d,-1)
WHERE b.d IS NULL AND c.d IS NOT NULL AND d.d IS NULL GROUP BY a.d) allstreaks;
However, repeatedly creating views for different users every time I run this check seems pretty inefficient. Is there a way in MySQL to perform this computation in a single query, without creating views or repeatedly calling the same subqueries a bunch of times?
This solution seems to perform quite well as long as there is a composite index on users_id and beverages_id -
SELECT *
FROM (
SELECT t.*, IF(#prev + INTERVAL 1 DAY = t.d, #c := #c + 1, #c := 1) AS streak, #prev := t.d
FROM (
SELECT DATE(timestamp) AS d, COUNT(*) AS n
FROM beverages_log
WHERE users_id = 1
AND beverages_id = 1
GROUP BY DATE(timestamp)
HAVING COUNT(*) >= 5
) AS t
INNER JOIN (SELECT #prev := NULL, #c := 1) AS vars
) AS t
ORDER BY streak DESC LIMIT 1;
Why not include user_id in they daycounts view and group by user_id and date.
Also include user_id in view t.
Then when you are queering against t add the user_id to the where clause.
Then you don't have to recreate your views for every single user you just need to remember to include in your where clause.
That's a little tricky. I'd start with a view to summarize events by day:
CREATE VIEW BView AS
SELECT UserID, BevID, CAST(EventDateTime AS DATE) AS EventDate, COUNT(*) AS NumEvents
FROM beverages_log
GROUP BY UserID, BevID, CAST(EventDateTime AS DATE)
I'd then use a Dates table (just a table with one row per day; very handy to have) to examine all possible date ranges and throw out any with a gap. This will probably be slow as hell, but it's a start:
SELECT
UserID, BevID, MAX(StreakLength) AS StreakLength
FROM
(
SELECT
B1.UserID, B1.BevID, B1.EventDate AS StreakStart, DATEDIFF(DD, StartDate.Date, EndDate.Date) AS StreakLength
FROM
BView AS B1
INNER JOIN Dates AS StartDate ON B1.EventDate = StartDate.Date
INNER JOIN Dates AS EndDate ON EndDate.Date > StartDate.Date
WHERE
B1.NumEvents >= 5
-- Exclude this potential streak if there's a day with no activity
AND NOT EXISTS (SELECT * FROM Dates AS MissedDay WHERE MissedDay.Date > StartDate.Date AND MissedDay.Date <= EndDate.Date AND NOT EXISTS (SELECT * FROM BView AS B2 WHERE B1.UserID = B2.UserID AND B1.BevID = B2.BevID AND MissedDay.Date = B2.EventDate))
-- Exclude this potential streak if there's a day with less than five events
AND NOT EXISTS (SELECT * FROM BView AS B2 WHERE B1.UserID = B2.UserID AND B1.BevID = B2.BevID AND B2.EventDate > StartDate.Date AND B2.EventDate <= EndDate.Date AND B2.NumEvents < 5)
) AS X
GROUP BY
UserID, BevID