I am trying to get the last of month, and in order to that i have written the following, to calculate the no. of days between today and the last date.
select datediff(DAY,GETDATE(),dateadd(m,1,getdate()))-GETDATE()
the bold part gives me the no. of days between today and a month from today, say 30 or 31. and then I am subtracting today's date from 30 or 31, which is " -getdate() "
The output for the above query is
1786-06-06 11:44:30.540
Could you please explain what is happening in the query? I am not looking for a solution, I would like to know how is SQL-Server interpreting the query.
Thanks. :)
The bold part of the expressions does not return a date, it returns a number of days:
31
Convert that to a datetime:
SELECT CONVERT(DATETIME, 31);
This is 31 days after day 0 (1900-01-01):
1900-02-01
Now, subtract GETDATE() as an integer (41512 days after day 0):
SELECT 31 - 41512 = -41481
Now add -41481 days to day 0:
SELECT DATEADD(DAY, -41481, 0);
-- or
SELECT DATEADD(DAY, -41481, '19000101');
Or:
SELECT CONVERT(DATETIME, 31 - CONVERT(INT, GETDATE()));
Now, I strongly recommend a couple of things:
Don't use implicit date math. #date_var_or_col - 1 for example fails with new data types like DATE and DATETIME2.
Don't use shorthand like m. If you mean MONTH, just take the massive productivity hit and type out MONTH. To see why, tell me if this provides the results you expect:
SELECT DATEPART(y, GETDATE()), DATEPART(w, GETDATE());
I am subtracting today's date from 30 or 31, which is " -getdate() "
Sounds like you understand exactly what is happening, but maybe don't understand the results.
You are implicitly converting GETDATE() to a number, which represents the number of days (and fractional days) since 1/1/1900 12:00:00 AM
When you "subtract" GETDATE() (41,511 as of 8/27/2013) from 30 or 31 you get an answer of -41,480, or 41,480 days before 1/1/1900, which would be about 6/6/1786 (plus or minus a few hours for the fractional part).
Related
I have inherited a query from an old MS Access DB and cannot for the life of me figure out what was trying to be done in this date parameter function. I normally only use SQL and this seems a bit different. Can any one assist in describing what this logic is doing?
use pdx_sap_user
go
select po_number,
po_issue_date
from vw_po_header
where po_issue_date > getDate() And PO_issue_date < DateAdd("d",-1,DateAdd("m",8,DateAdd("d",-(Day(getDate())-1),getDate())))
You can de-obfuscate it a lot by using DateSerial:
where
po_issue_date > getDate() And
po_issue_date < DateSerial(Year(getDate()), Month(getDate()) + 8, 0)
First: there is no getDate() function in Access. Probably it should be Date() which returns the current date.
Now starting from the inner expression:
Day(Date()) returns the current day as an integer 1-31.
So in DateAdd("d", -(Day(Date())-1), Date()) from the current date are subtracted as many days as needed to return the 1st of the current month.
Then:
DateAdd("m", 8, DateAdd("d", -(Day(Date())-1), Date()))
adds 8 months to the the 1st of the current month returning the 1st of the month of the date after 8 months.
Finally:
DateAdd("d", -1,...)
subtracts 1 day from the date returned by the previous expression, returning the last day of the previous month of that date.
So if you run today 13-Sep-2019 this code, the result will be:
30-Apr-2020
because this is the last day of the previous month after 8 months.
I think the following:
Take the current date
Substract the current day of month -1 to get the first day of current month
Add 8 month to this
Substract 1 day to get the last day of the previous month
So it calculates some deadline in approx 8 months.
But I wonder how a PO issue date can be in the future...
I'm developing a SQL Query, as a restriction, I want that the query returns data from the first day of the last month until now.
For example: If the query is executed today, the query will only return data entered from 01/03/2019 until today.
To do this, i created the following restriction:
...
SF1010.F1_DTDIGIT>=concat(YEAR(GETDATE()),'0',month(GETDATE())-1,'01') AND
...
The problem is in the months 01, 11 and 12:
If the month is "11", the algorithm will return "1901001" and not "191001".
If the month is "01", the algorithm will return "190001" and not "181201".
Thanks for any help.
SF1010.F1_DTDIGT BETWEEN $yourDate AND date_add($yourDate,interval -DAY($yourDate)+1 DAY)
This gets dates between your date and the first day of the month. first day logic works by subtracting the DAY part to get first of month.
This query will do the comparison of your DTDIGIT with the first day of the previous month in the DATE format:
SF1010.F1_DTDIGIT >= STR_TO_DATE(CONCAT(YEAR(DATE_SUB(NOW(), INTERVAL 1 MONTH)),'-',MONTH(DATE_SUB(NOW(), INTERVAL 1 MONTH)),'-','1'), '%Y-%m-%d')
Explanation
DATE_SUB(NOW(), INTERVAL 1 MONTH) returns the date exactly one month ago. We use that date to get the previous month
YEAR() and MONTH() functions use the date explained above
STR_TO_DATE() function converts a string representing a date to the
MySQL DATE format, using the mask (in this example, it's
'%Y-%m-%d').
How about this?
SF1010.F1_DTDIGT >= date_add(date_add(curdate(), interval 1 - day(curdate()) day), interval -1 month)
This assumes the date is not in the future. You can add another condition if that is possible.
If you happen to be using SQL Server, you can do this weird form of date arithmetic:
SF1010.F1_DTDIGT >= dateadd(month, datediff(month, 0, getdate()) - 1, 0)
I am trying to write a variable using the dateadd and datediff that shows the last two days of previous month. One variable will be the second to last day of the previous month, the one I am having trouble with. The other will be the last day of the previous month, the one I was able to get. I am using SQL Server.
I've tried looking for it on Stack and I have only seen the last day of the previous month given and NOT the second to last day. I tried learning the dateadd and datediff, (which I still want to do).
This is what I tried so far:
Declare #CurrentMonth as date = '3/1/2019'
Declare #SecLastDayPrevMonth as date = DATEADD(MONTH, DATEDIFF(MONTH, 0, #currentmonth), -2)
Declare #LastDayPrevMonth as date = DATEADD(MONTH, DATEDIFF(MONTH, 0, #currentmonth), -1)
The results I am getting for the seclastdayPrevMonth is 2/28/2019. Instead I would want 2/27/2019
I am also getting 2/28/2019 for lastdayprevmonth which is what I want.
I am writing variables because the current month will change every month, and instead of having to update the other days I need within my query, I want to use variables so I am only updating the current month and everything else is flowing through.
And explanation as to why my dateadd/datediff is wrong and an explanation for why the correct dateadd/datediff is the way it is, will be very helpful
Why not refer to the last day when calculating the second last day? Also, your usage of DATEADD is very weird. The syntax is DATEADD(interval, increment, datetime)
Declare #recmonth as date = '3/1/2019'
Declare #LastDayPrevMonth as date = EOMONTH(DATEADD(MONTH, -1, #RecMonth))
Declare #SecLastDayPrevMonth as date = DATEADD(DAY, -1, #LastDayPrevMonth)
SELECT #SecLastDayPrevMonth, #LastDayPrevMonth
So we can calculate the last day of the previous month by subtracting one month from a date and then calling EOMONTH, which returns the last day of a given month. Then the second last day is just subtracting one day from that.
Yields:
SecLastDayPrevMonth LastDayPrevMonth
------------------- ----------------
2019-02-27 2019-02-28
As to "why", DATEDIFF() takes 3 arguments: datepart (string representation of a specific date part), startdate, enddate (both of which must be convertible to a date-ish object).
0 is essentially SQL's epoch, which, in this case is 1/1/1900. So the difference in months between 0 and 3/1/2019 is (119*12)+2 (+2 because we exclude March, since we aren't calculating a full month) = 1430 months difference.
Then, we are trying to add 2 months to our value. DATEADD() takes 3 arguments: datepart, number, date. But, in the example, you are adding 1430 months to whatever date -2 gets converted to (in this case, I believe it would be 12/30/1899, or 2 days before epoch). So, 1430 months after 12/30/1899 would be 2/30/2019, but February only has 28 days in 2019, so it returns 2/28/2019. In a Leap Year, it probably would return 2/29/2019.
To get your #LastDayPrevMonth and #SecLastDayPrevMonth with only DATEDIFF() and DATEADD(), you just need to change your calculations a little.
First thing you want to do is find the First Day of your Given Month. That can be done with DATEADD(month,DATEDIFF(month,0,#CurrentDate),0). We're essentially using the same thing we used above to calculate the number of months since epoch, but then we are adding those months back to epoch.
Now that we know the First Day of the Given Month, all we have to do is subtract days to get a day from the prior month.
So,
DECLARE #CurrentDate date = '2019-03-15' ; -- Changed it to something in the middle of the month.
DECLARE #FirstDayOfGivenMonth = DATEADD(month,DATEDIFF(month,0,#CurrentDate),0) ; -- 3/1/2019
DECLARE #LastDayOfPrevMonth date = DATEADD(day,-1,#FirstDayOfThisMonth) ; -- 2/28/2019
DECLARE #SecLastDayOfPrevMonth date = DATEADD(day, -2, #FirstDayOfThisMonth) ; -- 2/27/2019
SELECT #LastDayOfPrevMonth AS LDPM, #SecLastDayOfPrevMonth AS SLDPM ;
DECLARE #FourDaysLeftInPrevMonth date = DATEADD(day, -4, #FirstDayOfThisMonth) ; -- 2/25/2019
SELECT #FourDaysLeftInPrevMonth AS FourDaysLeftPrev ;
Granted, since SQL 2012, this can all be accomplished much easier with the EOM() function to get to the last day of a month. But if you only could use the two original functions from your original question, this would be one way to get to your needed values.
I'm executing the next query in sql server 2012.
select *
from table
where date > convert(date, '2015/02/12')
order by date asc
but I'm getting the next set:
2015-02-12 06:40:42.000
2015-02-12 06:45:44.000
2015-02-12 06:48:15.000
2015-02-12 07:06:28.000
2015-02-12 07:26:46.000
...
I can fix this by changing the date to '2015/02/13', but I have the doubt about this behavior, why am I getting dates from feb 12 when I am specifying that I need only later dates ?. I also tried using cast('2015/02/12' as date), but I could not have the answer I was looking for
Because dates without times are intepreted as 12:00 midnight on that date. If you want only dates after February 12, 2015, then select all dates greater than or equal to February 13, 2015 (which again will be interpreted as midnight on February 13th).
select *
from table
where date >= convert(date, '2015/02/13')
order by date asc
why am I getting dates from feb 12 when I am specifying that I need only later dates ?
You're not specifying that you need only dates after Feb 12. You're asking for every row in which the value in the "date" column is greater than '2015-02-12'.
The value '2015-02-12 06:40:42.000' is greater than '2015-02-12'.
When comparing the date 2015/02/12 with your datetime data, this will implicitly compare the converted date 2015-02-12 00:00:000, the date at the beginning of the day with all of your data in column date.
But you are actually comparing datetime data, which has a time part as well, which gets compared.
And because you're comparing the beginning of the day (2015-02-12 00:00:000) with a value which is after it, for example 2015-02-12 06:40:42, all of the dates from will be displayed, because 6:40 AM is after (greater than) 0:00 AM.
Try this:
SELECT *
FROM TABLE
WHERE DATE >= DATEADD(SECOND, -1, '2015/02/13')
jarlh is right, though I'll clarify a little. Each of the "dates" you show above fall after 12:00 midnight starting 2015-02-12. They are actually timestamps.
If you don't want to see anything for the day specified in the filter, you add a day and use the greater-than-or-equal-to (>=) operator.
SELECT *
FROM table
WHERE (date >= DATEADD(d, 1, CONVERT(date, '2015/02/12')))
ORDER BY date ASC
Is there a way to get the week number of a date with SQL that is database independent?
For example to get the month of a date I use:
SELECT EXTRACT(MONTH FROM :DATE)
But the EXTRACT function doesn't know about weeks in SQL92.
Please pay attention to the fact that I want a solution that is database independent! Do not misinterpret this as a question regarding MS SQL Server.
There doesn't appear to be a single standard SQL function to extract the week number from a date - see here for a comparison of how different SQL dialects can extract different dateparts from date fields.
You can try this.
declare #date datetime
select #date='2013-03-15 00:00:00'
select 'Week No: '+ convert(varchar(10),datepart(wk,#date)) as weekno
Try this one :
SELECT DATENAME(yy,GETDATE())+RIGHT(DATENAME(wk,GETDATE()),2)
To understand DATENAME, please follow this link : sqltutorials.blogspot.be/2007/05/sql-datename.html and for the right, suite101.com/article/sql-functions-leftrightsubstrlengthcharindex-a209089 . There are examples to better understand ;-) It will work on MS and other sql servers normally ;-)
The only db independent solution I see is to get the number of days between today and Jan 1 of curr. year. Then divide it by 7 and round it up. There is 73 days from Jan 1 till today, which gives 10.43 as week number. The ISO week number is 11.
Correction: the number of days between last day of the current week and Jan 1 of curr. year. In this case the ISO week is 10, and 68/7 = 10 (rounded).
The best idea I found is
SELECT ROUND(((DAY(NOW())-1)/7)+1)
select (DATEPART(yyyy , CAST(GETDATE() AS datetime)) * 100 +
DATEPART(ww , CAST(GETDATE() AS datetime))) as week