I'm trying to find out the time between certain fields in my tables. However cause I'm using Postgresql :(( I can't use the DATEDIFF function. I can't find any clear guides/ tutorials on the net which shows how to do a similar thing in Postgres so I need help doing the same thing but in Postgres
I'm assuming this query would work if I was using a RDBMS that supported the DATEDIFF function so basically my question is how can I change this so it works using features provided by Postgresql?
SELECT Question.ID,
Question.Status, COUNT (qUpdate.ID) AS NumberofUpdates,
DATEDIFF (Question.LoggedTime,MIN(qUpdate.UpdateTime)) AS TimeBeforeFirstUpdate,
DATEDIFF(Question.LoggedTime, MAX(qUpdate.UpdateTime)) AS TimeBeforeLastUpdate
FROM qUpdate
LEFT JOIN Question ON qUpdate.qID=Question.ID
WHERE Question.Status = 'closed' AND qUpdate.Update NOT NULL
GROUP BY Question.Status, Question.ID, Question.LoggedTime;
If you need more info or any clarification I'll responsd ASAP.
You don't need a "datediff" function.
Just subtract the two dates:
Question.LoggedTime - MIN(qUpdate.UpdateTime)
In case you don't know, but all that is documented online:
http://www.postgresql.org/docs/current/static/functions-datetime.html
You can use the age(<date1>, <date2>) function (instead of DATEDIFF).
This should work -
SELECT Question.ID,
Question.Status, COUNT (qUpdate.ID) AS NumberofUpdates,
age(Question.LoggedTime,MIN(qUpdate.UpdateTime)) AS TimeBeforeFirstUpdate,
age(Question.LoggedTime, MAX(qUpdate.UpdateTime)) AS TimeBeforeLastUpdate
FROM qUpdate
LEFT JOIN Question ON qUpdate.qID=Question.ID
WHERE Question.Status = 'closed' AND qUpdate.Update NOT NULL
GROUP BY Question.Status, Question.ID, Question.LoggedTime;
Note, if psql gives you this error - ERROR: date/time field value out of range, then you would need to choose an appropriate datestyle.
SELECT extract(year from age('2014-01-23', '1985-08-27'));
-- returns 28 years, my current age.
this gives you the time diff in seconds:
select extract(epoch from to_date::timestamp - from_date::timestamp)
Related
I am struggling with a SQL query.
My query looks something like this:
Select
Count(user-id),
sum(distinct(date),
Sum(characters-posted)
From (
Select
Date,
User-Id,
Session-Id,
Characters—posted,
Variant-id
From database-name
Where date between ‘2022-09-01’ and ‘2022-09-31’)
This works ok. But, there is another field in the table “mailing-list”, which is just 0 or 1. I want to only get activity for members from the date when they join the mailing list onwards, even if they then leave the list, so can’t just do “where mailing-list=1”.
How can I do this?
It's not obvious what works fine for you as it seems to be uncommon to sum dates, given it is a regular date format. Are you trying to get number of active dates? as for the bottom question you might.
As for your buttom line quesiton, it seems that you might want to use a cte or subselect in a join.
your query...
from db_name dbn
inner join (select user_id, min(date) date from database_name
where mailing_list = 1 group by 1) start_date
on start_date.user_id = dbn.user_id
and start_date.date <= dbn.date
That way you're only getting activity starting from the first time your users join the mailing list.
But I still think you have an error in your final query, check it out.
I'm try to count distinct value in some columns in a table.
i have a logic and i try to write in 2 way
But i get diffent results from this two query.
Can any one help to clarify me? I dont know what wrong is code or i think.
SQL
select count(distinct membership_id) from members_membership m
where date_part(year,m.membership_expires)>=2019
and date_part(month,m.membership_expires)>=7
and date_part(day,m.membership_expires)>=1
and date_part(year,m.membership_creationdate)<=2019
and date_part(month,m.membership_creationdate)<=7
and date_part(day,m.membership_creationdate)<=1
;
select count(distinct membership_id) from members_membership m
where m.membership_expires>='2019-07-01'
and m.membership_creationdate<='2019-07-01'
;
I actually think that this is the query you intend to run:
SELECT
COUNT(DISTINCT membership_id)
FROM members_membership m
WHERE
m.membership_expires >= '2019-07-01' AND
m.membership_creationdate < '2019-07-01';
It doesn't make sense for a membership to expire at the same moment it gets created, so if it expires on midnight of 1st-July 2019, then it should have been created strictly before that point in time.
That being said, the problem with the first query is that, e.g., the restriction on the month being on or before July would apply to every year, not just 2019. It is difficult to write a date inequality using the year, month, and day terms separately. For this reason, the second version you used is preferable. It is also sargable, meaning that an index on membership_expires or membership_creationdate can be used.
There is an issue with the first query:
select count(distinct membership_id) from members_membership m
where date_part(year,m.membership_expires)>=2019
and date_part(month,m.membership_expires)>=7
and date_part(day,m.membership_expires)>=1
and date_part(year,m.membership_creationdate)<=2019
and date_part(month,m.membership_creationdate)<=7
and date_part(day,m.membership_creationdate)<=1; -- do you think that any day is less than 1??
-- this condition will be satisfy by only 01-Jul-2019, But I think you need all the dates before 01-Jul-2019
and date_part(day,m.membership_creationdate)<=1 is culprit of the issue.
even membership_creationdate = 15-jan-1901 will not satisfy above condition.
You need to always use date functions on date columns to avoid such type of issue. (Your second query is perfectly fine)
Cheers!!
The reason could be due to a time component.
The proper comparison for the first query is:
select count(distinct membership_id)
from members_membership m
where m.membership_expires >= '2019-07-01' and
m.membership_creationdate < '2019-07-02'
--------------------------------^ not <= ---^ next day
This logic should work regardless of whether or not the "date" has a time component.
I'm struggling to get the correct result with this query:
select max(kts.my_date), kts.name
join ktt on ktt.someId = kts.someOtherId
where ktt.someId = 'example'
group by kts.name;
I have two (possibly stupid) questions:
Will this max() take time into account? I know that order by does if the dates are the same. Does max do the same?
This is connected to my previous question, but when I run the query above, if the dates are same, it orders it by the name. I want the latest date at the top. Do I need to put an order by clause for the date in? If so, using Max is pointless, right?
Thanks for the help.
Yes,
--2
select max(kts.my_date) over (partition by kts.name) as maxdate, kts.name
from -- chose your table
join ktt on ktt.someId = kts.someOtherId
where ktt.someId = 'example'
order by --chose here your column
give this a try
HI all,
i have one sql table and field for that table is
id
name
expireydate
Now i want only those record which one is expired within 45 days or 30 days.
how can i do with sql query .?
I have not much more exp with sql .
Thanks in advance,
If you are using mysql then try DATEDIFF.
for 45 days
select * from `table` where DATEDIFF(now(),expireydate)<=45;
for 30 days
select * from `table` where DATEDIFF(now(),expireydate)<=30;
In oracle - will do the trick instead of datediff and SYSDATE instead of now().[not sure]
In sql server DateDiff is quite different you have to provide unit in which difference to be taken out from 2 dates.
DATEDIFF(datepart,startdate,enddate)
to get current date try one of this: CURRENT_TIMESTAMP or GETDATE() or {fn NOW()}
You can use a simple SELECT * FROM yourtable WHERE expireydate < "some formula calculating today+30 or 45 days".
Simple comparison will work there, the tricky part is to write this last bit concerning the date you want to compare to. It'll depend of your environment and how you stored the "expireydate" in the database.
Try Below:-
SELECT * FROM MYTABLE WHERE (expireydate in days) < ((CURRENTDATE in days)+ 45)
Do not execute directly! Depending of your database, way of obtaining a date in days will be different. Go look at your database manual or please precise what is your database.
How would I go about doing a query that returns results of all rows that contain dates for current year and month at the time of query.
Timestamps for each row are formated as such: yyyy-mm-dd
I know it probably has something to do with the date function and that I must somehow set a special parameter to make it spit out like such: yyyy-mm-%%.
Setting days to be wild card character would do the trick but I can't seem to figure it out how to do it.
Here is a link to for quick reference to date-time functions in mysql:
http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html
Thanks
I think EXTRACT is the function you are looking for:
SELECT * FROM table
WHERE EXTRACT(YEAR_MONTH FROM timestamp_field) = EXTRACT(YEAR_MONTH FROM NOW())
you could extract the year and month using a function, but that will not be able to use an index.
if you want scalable performance, you need to do this:
SELECT *
FROM myTable
WHERE some_date_column BETWEEN '2009-01-01' AND '2009-01-31'
select * from someTable where year(myDt) = 2009 and month(myDt) = 9 and day(myDt) = 12