I have a table where each entry has a timestamp. I am using this timestamp to calculate e.g. the number of entries per day in the last week. However, I do not really care whether the results that I get represent a particular day. The actual goal is to divide the entries into 24h-bins that I can compare and see whether there has been any significant change over time. Furthermore, since I am working with almost real-time data, I would like to perform this analysis at any time and also take into account the most recent entries. If I would just group the entries per day and perform the query in the middle of the day then I would get a not particularly insightful result for the current day.
My idea was now to subtract the current time from the timestamp of the entries and then do the grouping by days. This way I could get 24h-bins each of which represents a full 24h period and the youngest one also contains the most recent entries.
Something like this:
created_on - current_time
Of course I cannot subtract a time from a timestamp. Is there a way to convert current_time into an interval? Or is there an entirely different approach that is easier?
Is there a way to convert current_time into an interval?
Yes, just cast it.
Note that the use of current_time is discouraged so it's better to use localtime instead.
You can do:
created_on - localtime::interval
But it seems you might just want to set the time part of the timestamp to 00:00:00 which you can do by using date_trunc()
date_trunc('day', created_on)
Related
I want to create a query in Oracle SQL that will grab records from a given time interval, during certain hours of the day, e.g. records between 10am to noon, in the past 10 days. I tried this, but it does not work:
select * from my_table where timestamp between
to_timestamp('2020-12-30','YYYY-MM-DD')
and
to_timestamp('2021-01-08','YYYY-MM-DD') and
timestamp between
to_timestamp('10:00:00','HH24:MI:SS')
and
to_timestamp('12:00:00','HH24:MI:SS')
where timestamp is of type TIMESTAMP. I have also thought of using a join, but I am struggling to find a way to filter on time of day.
Is there a way to filter using only the time, not the date, or a way to filter on time for every day in the interval?
select *
from my_table
where timestamp between to_timestamp('2020-12-30','YYYY-MM-DD')
and to_timestamp('2021-01-08','YYYY-MM-DD')
and timestamp - trunc(timestamp) between interval '10' hour
and interval '12' hour
If you don't need to include exactly noon (including no fractional seconds), you could also do
select *
from my_table
where timestamp between to_timestamp('2020-12-30','YYYY-MM-DD')
and to_timestamp('2021-01-08','YYYY-MM-DD')
and extract( hour from timestamp ) between 10 and 11
As an aside, I'd hope that your actual column name isn't timestamp. It's legal as a column name but it is a reserved word so you're generally much better off using a different name.
I have the following problem to solve. I have a hive table, that store events, and each event timestamp is stored as unix timestamp (e.g. 1484336244).
Every day I want to run a query that fetches yesterdays events.
How could I form this query in Hive?
So for example, today is the 9th February, I want to get only the events that occurred on the 8th February.
Subtract one day from current_date and compare it with the column converted to yyyy-MM-dd format.
date_add(current_date,-1) = from_unixtime(colName,'yyyy-MM-dd')
In one of my SQL queries, I am using
[... and z.READ_TIMESTAMP > TIMESTAMP_TO_EPOCH(TRUNC(SYSDATE-3)]
If I want the date to be exactly 5/31/2017, will I use 'SYSDATE' (date-n) function or some other expression? or how can a modify my query for 5/31/2017
If you want the date to be exactly 5/31/2017 then use TO_DATE() or TO_TIMESTAMP() depending on which data type you need (date or timestamp). As you are using SYSDATE already the the date data type should work.
-- e.g.
select
to_date('5/31/2017','mm/dd/yyyy')
, to_timestamp('5/31/2017','mm/dd/yyyy')
from dual
...
and z.READ_TIMESTAMP > TIMESTAMP_TO_EPOCH(to_date('5/31/2017','mm/dd/yyyy'))
HOWEVER
I suspect you may want more than just a way to establish a fixed date. For example are you asking for "how do I get that last day of the previous month?" which perhaps can be satisfied by using >= and the first day of current month like this:
...
and z.READ_TIMESTAMP >= TIMESTAMP_TO_EPOCH(trunc(sysdate,'MM'))
or if it really is the last day of the previous month can be achieved with a combination of LAST_DAY() and ADD_MONTHS()
and z.READ_TIMESTAMP >
TIMESTAMP_TO_EPOCH( last_day(add_months(trunc(sysdate,'MM'),-1)) )
Without knowing a great deal more about the nature of your data and query purpose please do note that each date you use when "truncated" also has the time set to 00:00:000 - so IF you data contains time within a day other than 00:00:00 then these 2 queries might NOT produce the same result
.... datetimecolumn > to_date('05/31/2017','mm/dd/yyyy') -- "a"
.... datetimecolumn >= to_date('06/01/2017','mm/dd/yyyy') -- "b"
For example "a" the entire 24 hour duration of 05/31/2017 would be included in the results, but for example "b" that same 24 hour duration would be excluded from results. In my experience the last day of any month isn't really the best method for locating date/time based data, instead usually it is the first day of the next month that produces the correct result.
I have problem converting number column to date, I did the following
SELECT to_date('12-30-1899 1:00:00','MM-DD-YYYY HH24:Mi:SS') + (createDate/1440)
FROM table_A;
and got the query result
10/17/5826 17:18
The month and date including hours and seconds is right but the year is different I got 5826. Its also the same for the other rows i got different results for year. I did follow some examples on this here. But still got wrong result. Can anyone help on this thanks.
The samples below are createDate column values:
1300844909778
1302831103113
1303210978316
1396963615616
Date arithmetic in Oracle assumes days. As it stands you are dividing a very large number by 1440 and adding that number of days to your starting date. That's why you're getting results in the far future.
So what value does createdate represent? It's clearly not an actual date. Your choice of 1440 as denominator suggests you think it's meant to be "number of minutes" but if the dates are so far out of expectation that is not it either.
I thought could be values represented in the Unix epoch because the numbers start with 13. Except that they're way too big. Current Unix timestamps should be ten digits. You've got thirteen digits.
Could they be Unix epoch plus milliseconds?
I have created a SQLfiddle to test this theory. Treating the first ten digits of your createdate values as seconds and adding that number to the Unix date produces sensible dates. Check it out.
So the theory holds water. But I doesn't help with your query. Adding two dates together doesn't make any sense. What are you actually trying to achieve? If your're looking for an interval you need to subtract the earlier date from the later one.
The createDate could be the number of milliseconds. It is just a guess. If so, then maybe this helps:
SELECT to_date('12-30-1899 1:00:00','MM-DD-YYYY HH24:Mi:SS') + (1300844909778/(1000*60*60*24))
FROM dual
/
3/21/1941 2:48:30 AM
I have two NSDate objects. One (call it date1) has timestamp in the future i.e 2012-07-16 12:00 and also this date is repeating daily. The other one (date2) has a timestamp also in the future i.e 2012-07-17 12:00.
Now I want to check if possibly date1 will clash with date2. Obviously it will not clash at 2012-07-16 12:00 but the day after (since it's repeating daily) it will clash with date2.
How could I implement this check?
First check if the events would overlap on any date, i.e. using only the starting time and length of the events. If they do, then check if the dates are the same, or if the earlier of the dates is for an event that repeats enough times to occur on the date of the second event.
To compare the times you can use something like this to extract the hours and minutes from the NSDates: How do I get hour and minutes from NSDate?
For the second check you can first use NSDate's compare, followed by a timeIntervalSinceDate which you feed into something like this: How do I break down an NSTimeInterval into year, months, days, hours, minutes and seconds on iPhone? to get the number of days between the two dates, which you then can compare against the repeat count of the event.