select * from table
where Date BETWEEN DATEADD(dd, DATEDIFF(dd, 84, GETDATE()),0)
and DATEADD(dd, DATEDIFF(dd, 77, GETDATE()),0)
Can someone please explain what this query is doing? Specifically, what is the function of DATEADD and DATEDIFF in this query?
They're trying to get the membership renewals between 84 and 77 days ago, stripping out the time.
GETDATE() returns the datetime but the user isn't interested in the time.
DATEDIFF(dd, 84, GETDATE()) gets the number of days between the current date and the 84th day after Jan 1, 1900.
DATEADD(dd, # days from above, 0) adds those number of days to Jan 1, 1900.
The net is you get 84 days ago at 00:00:00 AM.
If you just did DATEADD(dd, -84, GETDATE()) then you'd have 84 days ago + the current time.
Other ways to do the same thing are to cast the datetime to a date (assuming MS SQL Server).
.. CAST((GETDATE() - 84) AS DATE)
.. CAST(DATEADD(day, -84, GETDATE()) as DATE)
Your expression is using SQL Server syntax to convert a datetime to a date (that is, to remove the date component. The format is quite arcane, because the expression is doing getdate() - 84 as an integer and then adding this to the 0 date. The elimination of the "time" component occurs because the datediff() returns an integer.
I don't think this will work in HQL. For instance, the dd should be 'dd' and HQL has a different method of getting the current date.
And, in more recent versions of SQL Server, you can just do cast(getdate() - 84 as date).
Related
I wish to pull three years of data from a database but right now I have to specify the dates in a number of sections in my code using a between statement:
BETWEEN '2015-10-01' AND '2018-09-30'
Since the database only contains valid data from the previous month backwards, I wish to take the end of the last month and go back three years.
I found this tutorial where the author shows how to do this in SQL server and I've tried to adapt it but my RDBMS is throwing errors in the datediff function
----Last Day of Previous Month
SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0))
LastDay_PreviousMonth
My code looks as follows but I the error I am seeing is about converting 0 to a date.
DECLARE #date DATE
SET #date = getdate()
SELECT dateadd(second,-1,dateadd(mm, DATEDIFF(m,0,GETDATE()),0))
If anyone has any suggestions I would be very grateful for your guidance.
In your WHERE clause, you could use this condition:
DATEDIFF(month, [YourDateColumn], GETDATE()) BETWEEN 1 AND 36
Your current code looks good without any error, but you can use EOMONTH() instead.
However, the difference would be in return types your code would return date-time while eomonth() would return date only.
DECLARE #date DATE
SET #date = getdate()
SELECT EOMONTH(#date, -1)
Don't use between and the job becomes far easier. Use less than the first day of the current month which accurately locates everything before that date (instead of last day of previous month). Subtract 3 years from that same date and use >= for the starting point.
Select *
From yourtables
where datecol >= dateadd (year,-3,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0) )
And datecol < DATEADD(mm,DATEDIFF(m,0,GETDATE()),0)
Please don't use any solution that use 23:59:59 as the end of a day. It is not the end of a day and several data types now support sub-second time precision.
If you really cannot use zero in the date functions simply use the base date of '1900-01-01' instead
SELECT
DATEADD(YEAR, -3, DATEADD(mm, DATEDIFF(m, 0, GETDATE()), '1900-01-01'))
, DATEADD(mm, DATEDIFF(m, 0, GETDATE()), '1900-01-01')
;
This should also work (it does in this demo here):
SELECT
DATEADD(YEAR, -3, DATEADD(mm, DATEDIFF(m, 0, GETDATE()), 0))
, DATEADD(mm, DATEDIFF(m, 0, GETDATE()), 0)
;
I have a date column like this 7/24/2017 and when I write the below where clause I get results from hour 7/24/2017 1:00:00.000 AM. I need to get this from 7/24/2017 12:00:00.000 AM. How should this where clause me modified. Please check the following code
Date>= DATEADD(day, -1, convert(date, GETDATE())) and
Date< DATEADD(day, +0, convert(date, GETDATE()))
There doesn't appear to be anything wrong with your code. Are you certain your data contains any times before 1am? Are you certain you appreciate how your SQLServer will format those times/represent them to you?
See this SQLFIDDLE: http://sqlfiddle.com/#!6/047cc/11
Optimisations: you don't need to dateadd a value of 0. You can also subtract 1.0 from a date to get the day earlier and it's a bit less wordy than DATEADD. It works because internally dates are represented as floating point numbers of the number of days since a point in time:
[Date] >= convert(date, GETDATE() -1.0) and
[Date] < convert(date, GETDATE())
I have the following sql which returns the date of last monday.
SELECT DATEADD(wk, DATEDIFF(wk, 6, GETDATE()), 0) //2017-05-15 00:00:00.000
However in trying to understand how this has been worked out, I'm confused
as to what the 6124 returned by the following represents
SELECT DATEDIFF(wk, 6, GETDATE())
It's only last week why is it such a high number?
Also how can the offset be a fixed number and still be able to work out the date of the previous monday
That's sunday of Jan of 1900...
SELECT
DATEDIFF(wk, '1/1/1900','5/20/2017'),
DATEDIFF(wk, '1/1/1900',GETDATE())
Specifically, they are using DATETIMEOFFSET instead of an actual DATETIME which is an acceptable parameter of DATEDIFF
So to answer you question, that's the number of weeks (since you specified wk) from the first Sunday in January 1900 to the current day.
The parameter of 6 for startdate in the datediff is just another way to reduce the output by one week, so it returns how many weeks since 1900-01-06 instead of 1900-01-01 (difference of one).
These two statements will return the same result:
select dateadd(week, datediff(week, 6, getdate()),0)
select dateadd(week, datediff(week, 0, getdate())-1,0)
Just this part: datediff(week, 6, getdate() returns the number of weeks (6,124) since 1900-01-06 which when added to a date of 1900-01-01 gives you the start of last week.
If I have a date value like 2010-03-01 17:34:12.018
What is the most efficient way to turn this into 2010-03-01 00:00:00.000?
As a secondary question, what is the best way to emulate Oracle's TRUNC function, which will allow you to truncate at Year, Quarter, Month, Week, Day, Hour, Minute, and Second boundaries?
To round to the nearest whole day, there are three approaches in wide use. The first one uses datediff to find the number of days since the 0 datetime. The 0 datetime corresponds to the 1st of January, 1900. By adding the day difference to the start date, you've rounded to a whole day;
select dateadd(d, 0, datediff(d, 0, getdate()))
The second method is text based: it truncates the text description with varchar(10), leaving only the date part:
select convert(varchar(10),getdate(),111)
The third method uses the fact that a datetime is really a floating point representing the number of days since 1900. So by rounding it to a whole number, for example using floor, you get the start of the day:
select cast(floor(cast(getdate() as float)) as datetime)
To answer your second question, the start of the week is trickier. One way is to subtract the day-of-the-week:
select dateadd(dd, 1 - datepart(dw, getdate()), getdate())
This returns a time part too, so you'd have to combine it with one of the time-stripping methods to get to the first date. For example, with #start_of_day as a variable for readability:
declare #start_of_day datetime
set #start_of_day = cast(floor(cast(getdate() as float)) as datetime)
select dateadd(dd, 1 - datepart(dw, #start_of_day), #start_of_day)
The start of the year, month, hour and minute still work with the "difference since 1900" approach:
select dateadd(yy, datediff(yy, 0, getdate()), 0)
select dateadd(m, datediff(m, 0, getdate()), 0)
select dateadd(hh, datediff(hh, 0, getdate()), 0)
select dateadd(mi, datediff(mi, 0, getdate()), 0)
Rounding by second requires a different approach, since the number of seconds since 0 gives an overflow. One way around that is using the start of the day, instead of 1900, as a reference date:
declare #start_of_day datetime
set #start_of_day = cast(floor(cast(getdate() as float)) as datetime)
select dateadd(s, datediff(s, #start_of_day, getdate()), #start_of_day)
To round by 5 minutes, adjust the minute rounding method. Take the quotient of the minute difference, for example using /5*5:
select dateadd(mi, datediff(mi,0,getdate())/5*5, 0)
This works for quarters and half hours as well.
If you are using SQL Server 2008+, you can use the Date datatype like this:
select cast(getdate() as date)
If you still need your value to be a DateTime datatype, you can do this:
select cast(cast(getdate() as date) as datetime)
A method that should work on all versions of SQL Server is:
select cast(floor(cast(getdate() as float)) as datetime)
Try:
SELECT DATEADD(dd, DATEDIFF(dd, 0, GETDATE()), 0)
UPDATE: answer on the second question:
for years you could use a little bit modified version of my answer:
SELECT DATEADD(yy, DATEDIFF(yy, 0, GETDATE()), 0)
for quarter:
SELECT DATEADD(qq, DATEDIFF(qq, 0, GETDATE()), 0)
and so on.
I checked, up to minutes - it's OK. But on seconds I've got an overflow message:
Difference of two datetime columns
caused overflow at runtime.
One more update: take a look to the following answer to the same question
This is late, but will produce the exact results requested in the post. I also feel it is much more intuitive than using dateadd, but that is my preference.
declare #SomeDate datetime = '2010-03-01 17:34:12.018'
SELECT
DATEFROMPARTS(
YEAR(#SomeDate)
,MONTH(#SomeDate)
,'01'
) AS CUR_DATE_FROM_PARTS
,DATETIMEFROMPARTS(
YEAR(#SomeDate)
,MONTH(#SomeDate)
,'01' --DAY(#SomeDate)
,'00' --DATEPART(HOUR,#SomeDate)
,'00' --DATEPART(MINUTE,#SomeDate)
,'00' --DATEPART(SECOND,#SomeDate)
,'00' --DATEPART(MILLISECOND,#SomeDate)
) AS CUR_DATETIME_FROM_PARTS
,#SomeDate AS CUR_DATETIME
,YEAR(#SomeDate) AS CUR_YEAR
,MONTH(#SomeDate) AS CUR_MONTH
,DAY(#SomeDate) AS CUR_DAY
,DATEPART(HOUR,#SomeDate) AS CUR_HOUR
,DATEPART(MINUTE,#SomeDate) AS CUR_MINUTE
,DATEPART(SECOND,#SomeDate) AS CUR_SECOND
,DATEPART(MILLISECOND,#SomeDate) AS CUR_MILLISECOND
FROM Your_Table
Truncated Date: 2010-03-01
Truncated DateTime: 2010-03-01 00:00:00.000
DateTime: 2010-03-01 17:34:12.017
Not sure if this is the most efficient, but I like the simplicity in using the following where #SomeDate is your field.
Concat(Year(#SomeDate), '-', Month(#SomeDate), '-', '01')
If you want to truncate a date to the start of the week in a way that is independent of SET DATEFIRST you can:
--change a date backwards to nearest Monday
DATEADD(DAY, (DATEPART(dw, '2001-01-01') - DATEPART(dw, YOUR_COLUMN)-7)%7, YOUR_COLUMN)
Breaking this down:
DATEPART(dw, '2001-01-01') - DATEPART(dw, YOUR_COLUMN): the dw of a known Monday (2001-01-01 was a Monday) minus the dw of your date, effectively giving the "number of days difference between your date and Monday" or "how many days back do we have to scroll your date to make it into Monday"
( ... -7)%7 - we subtract 7 from it and modulo the result by 7.
We do this because if e.g. DATEFIRST is 7 (Sunday), and your date column is Sunday then your dw is 1, and your known Monday is 2.
This means the result of the dw_for_known_monday - dw_for_your_date is +1 rather than -6
This would then mean that DATEADD will roll your date forwards to the following Monday rather than backwards to the previous Monday
If we subtract 7 off it then the result would definitely be negative, but then we wouldn't want your Mondays (which are 0 days different from the known Monday) to end up doing a DATEADD of -7, so we modulo the result by 7.
This turns any problematic -7 into 0, which means your DATEADD will only ever have a "number of days" argument between -6 and 0
DATEADD(DAY, (DATEPART(dw, '2001-01-01') - DATEPART(dw, YOUR_COLUMN)-7)%7, YOUR_COLUMN) - we then DATEADD the (negative) number of days from the above step
If you want to roll your date backwards to e.g. a Sunday, change the date 2001-01-01 to a date that is a known Sunday (like 2000-12-31), etc
I am trying to get current date - 6 days. That is easy.
Now I am trying to get current date - 6 days + 12:01 AM.
So if today is 3-2-2012 11:14 AM.
I want to get 2-25-2012 12:01 AM
These 2 selects will give me current date - 6, but will not reset the time to 12:01 AM
select getdate()-6
SELECT DATEADD(day, -6, CURRENT_TIMESTAMP);
SELECT DATEADD(minute, 1, DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()) - 6, 0))
is equivalent to
SELECT DATEADD(minute, 1, DATEADD(DAY, DATEDIFF(DAY, '19000101', GETDATE()) - 6, '19000101'))
I think you will find this option faster and more flexible than the varchar implementations. by keeping the data types as they are, you don't have to worry about the vagaries of the cast/convert results.
See Louis Davidson for one of the full explainations:
http://sqlblog.com/blogs/louis_davidson/archive/2011/02/09/some-date-math-fun.aspx
Using the following will give you the result in a datetime format:
SELECT CAST(Convert(varchar(10), DateAdd(d, -6, getdate()), 101)
+ ' 12:01 AM' as datetime)
Result: 2012-02-25 00:01:00.000
Once you have the datetime that you want, you can convert it to many different formats.
Or you can do the following which is in a varchar format:
select Convert(varchar(10), DateAdd(d, -6, getdate()), 110) + ' 12:01 AM'
which results in 02-25-2012 12:01 AM
One less conversion that #Phil Helmer's solution:
SELECT DATEADD(DAY, DATEDIFF(DAY, '19000101', GETDATE()), '1899-12-26T12:01:00')
Since some people are apparently unaware that everything "to the right" of the element specified in that DATEADD/DATEDIFF pair is effectively taken from the right-hand constant. Everything "to the left" (and including the actual element) can be used to achieve offsetting effects.
(The above left/right are assuming that the entire datetime value is being interpreted with year to the left and milliseconds to the right, with all intermediate values in "size" order)
Edited - I've also updated my answer to subsume the -6 into the right-hand value. Its possible to create all kinds of offsetting by picking suitable values for the two constants.
The relationship between the two datetime constants specified in the expression ought to be expressed, at least in a comment alongside the usage. In the above, I'm using 1/1/1900 as a base point, and computing the number of midnight transitions between then and now (as DATEDIFF always works). I'm then adding that number of days onto the point in time 6 days earlier (e.g. 26/12/1899) at exactly 00:01 in the morning...
SELECT DATEADD(dd, -6, DATEDIFF(dd, 0, GETDATE())) + '12:01'