In a SQL Server query, I am currently using the clause
WHERE
DAY(trade_date) = DAY(GETDATE()) - 1
AND MONTH(trade_date) = MONTH(GETDATE())
AND YEAR(trade_date) = YEAR(GETDATE())
to query my data from the previous day.
It is working fine right now but my question is if, for example, on 8/1/2021, SQL Server will try to get data from 8/0/2021 or if it will know to get data from 7/31/2021.
If this query won't work what could I use instead? Thanks!
I would recommend using proper date comparison logic - instead of breaking it down to day, month and year. Also, it is recommended to use proper date arithmetic functions like DATEADD instead of just - 1 on your date values (never sure what that -1 stands for: minus one day? Week? Month? Hour?).
And lastly - I would also recommend using SYSDATETIME() instead of GETDATE() since the latter always returns a DATETIME datatype - which should be on its way out, and you should use DATE (if you don't need to time portion), or DATETIME2(n) (if you do need the time portion) since those are more efficient and have fewer limitations compared to DATETIME.
If your trade_date is a DATE column (as it probably should be), just use:
WHERE
trade_date = DATEADD(DAY, -1, SYSDATETIME())
and if it's not a DATE - just cast it to a date as needed:
WHERE
CAST(trade_date AS DATE) = DATEADD(DAY, -1, CAST(SYSDATETIME() AS DATE))
I have a function which is working fine in MySQL
round((now()-ts/60) as tdiff
(round the result of subtracting the current datetime from ts (also a datetime) divided by 60)
Attempting (and failing) to convert this for SQL Server.
Tried -
round((GETDATE()-ts/60) as tdiff
but that results in round function requires 2 or 3 parameters (which to me it does), so modified to -
round((GETDATE()-ts/60,0) as tdiff
but that results in the datatypes (GETDATE and ts) are incompatible in the subtract operator.
So then I attempted to cast both GETDATE and ts as date and that made no difference.
ts is a conventional datetime i.e.
2918-04-20 11:05:09 and I assumed GETDATE returned the same format.
As an example if GETDATE is today and ts is 2018-04-20 11:05:09 then tdiff is
6850891 (round effectively removes the dashes and colons and concatenates the datetime producing 20180420110509 for 2018-04-20 11:05:09 and 20180831164000 for 2018-08-31 16:40:00 and then divides by 60 to get 6850891.
Is there a remedy for this?
Regards, Ralph
GETDATE(), as per the documentation, returns a datetime. A datetime is accurate to 1/300 of a second, and it's accuracy cannot be changed.
If you want the time accurate to a second, you need to convert to a datetime2(0):
SELECT CONVERT(datetime2(0),GETDATE());
Also, however, don't use syntax like GETDATE()-ts. use the functions DATEADD and DATEDIFF for date maths.
I've no idea what GETDATE()-ts/60 is trying to acheive. Perhaps the number of minutes between the 2? DATEDIFF counts the "ticks" between 2 dates/times, thus DATEDIFF(MINUTE,'00:00:59','00:01:00') would return 1, despite there only being 1 second between the 2 times. This is because the minute value has "ticked" once (from 0 to 1). Therefore you might want to use DATEDIFF(SECOND,'00:00:59','00:01:00') / 60. This would return 0, as 1 / 60 in integer math is 0 (as is 59 / 60).
I think you want to use the DATEDIFF function:
DATEDIFF ( datepart , startdate , enddate )
DATEDIFF ( second, ts, GETDATE())
DATEDIFF ( second, ts, GETDATE())
DATEDIFF ( minute, ts, GETDATE())
DATEDIFF ( hour, ts, GETDATE())
The first argument tells it which increment of time to return.
If you are trying to find the difference between two values, then use datediff(). For instance:
select datediff(day, getdate(), ts)
gets the difference in days.
date_diff() or a related function would also be the right approach in MySQL.
sorry, I don't know if I have understand the question, you need to do date-date/60 and round the result?
In this case you have to change the minus ("-") with the DATEDIFF("Type return example DAYS", GETDATE(), ts).
So you will have ROUND((DATEDIFF(DAY,GETDATE(),ts)/60,0)
Please try and let me know if it will works for you
Bye
I need help. Pervasive DB stored dates in days. For example 719311 would be the amount of days from 01/01/0001 to May 28 1970. So May 28 1970 is the date represented in pervasive when looking at 719311.
You can use SQL Servers dateadd feature for this. However the values in Pervasive are much too large to add to the base date of 0 (1900-01-01).
To work around that I used the known integer/date provided and calculated the delta between 0001-01-01 and 1900-01-01 - which is 693597. This value is static, and can be subtracted from each Pervasive value and used in the dateadd. The result can then be added to 1900-01-01.
-- GET BASE DATE OF 0
SELECT CONVERT(DATETIME,0)
-- CALCULATE DIFF FROM 0 TO A KNOWN DATE...
SELECT DATEDIFF(DD,0,'1970-05-28')
--SUBTRACT ABOVE DIFF FROM KNOWN INTEGER FOR SAID DATE... THIS IS OUR DELTA
SELECT 719311-25714
-- ADD THE INTEGER OF SAID DATE, MINUS THE ABOVE DELTA TO 0 TO CONFIRM WE GET THE KNOWN DATE.
SELECT DATEADD(DD,719311-693597,0)
-- USING VARIABLES, LEAVE #DELTA AS A STATIC VALUE, JUST UPDATE #PERVASIVE
DECLARE #PERVASIVE INT, #DELTA INT
SET #PERVASIVE=719312
SET #DELTA=693597
SELECT DATEADD(DD,#PERVASIVE-#DELTA,0)
select datediff(day,'0001-01-01','1753-01-01') + 2
select 719311 - 639907 -- sql
select dateadd(day,79404,'1753-01-01')
dateadd() function cannot work with a date older than '1753-01-01', so you need the 719311 days minus the 639907 days. The difference you can than plug into the dateadd() function.
You should get this 1970-05-28 00:00:00.000
Another alternative is add days to a date datatype.
When I add 719311 days to '0001-01-01' I get '1970-05-30'
To get '1970-05-28' I have to remove 2 of those days.
select dateadd(day,719311-2,convert(date,'00010101'))
returns '1970-05-28'
I am running a select against a datetime column in SQL Server 2005. I can select only the date from this datetime column?
Best way is:
SELECT DATEADD(day, DATEDIFF(Day, 0, #ADate), 0)
This is because internally, SQL Server stores all dates as two integers, of which the first one is the ****number of days*** since 1 Jan 1900. (the second one is the time portion, stored as the number of seconds since Midnight. (seconds for SmallDateTimes, or milleseconds for DateTimes)
Using the above expression is better because it avoids all conversions, directly reading and accessing that first integer in a dates internal representation without having to perform any processing... the two zeroes in the above expression (which represent 1 Jan 1900), are also directly utilized w/o processing or conversion, because they match the SQL server internal representation of the date 1 jan 1900 exactly as presented (as an integer)..
*NOTE. Actually, the number of date boundaries (midnights) you have to cross to get from the one date to the other.
Yes, by using the convert function. For example:
select getdate(), convert(varchar(10),getdate(),120)
RESULTS:
----------------------- ----------
2010-05-21 13:43:23.117 2010-05-21
You can use the functions:
day(date)
month(date)
year(date)
Also the Datepart() function might be of some use:
http://msdn.microsoft.com/en-us/library/ms174420(SQL.90).aspx
DECLARE #dToday DATETIME
SET #dToday = CONVERT(nvarchar(20), GETDATE(), 101)
SELECT #dToday AS Today
This returns today's date at 12:00am : '2010-05-21 00:00:00.000'
Then you can use the #dToday variable in a query as needed
CONVERT (date, GETUTCDATE())
CONVERT (date, GETDATE())
CONVERT (date, '2022-18-01')
I don't know why the others recommend it with varchar(x) tbh.
https://learn.microsoft.com/de-de/sql/t-sql/functions/getdate-transact-sql
Which method provides the best performance when removing the time portion from a datetime field in SQL Server?
a) select DATEADD(dd, DATEDIFF(dd, 0, getdate()), 0)
or
b) select cast(convert(char(11), getdate(), 113) as datetime)
The second method does send a few more bytes either way but that might not be as important as the speed of the conversion.
Both also appear to be very fast, but there might be a difference in speed when dealing with hundreds-of-thousands or more rows?
Also, is it possible that there are even better methods to get rid of the time portion of a datetime in SQL?
Strictly, method a is the least resource intensive:
a) select DATEADD(dd, DATEDIFF(dd, 0, getdate()), 0)
Proven less CPU intensive for the same total duration a million rows by someone with way too much time on their hands: Most efficient way in SQL Server to get a date from date+time?
I saw a similar test elsewhere with similar results too.
I prefer the DATEADD/DATEDIFF because:
varchar is subject to language/dateformat issues
Example: Why is my CASE expression non-deterministic?
float relies on internal storage
it extends to work out first day of month, tomorrow, etc by changing "0" base
Edit, Oct 2011
For SQL Server 2008+, you can CAST to date i.e. CAST(getdate() AS date). Or just use date datatype so no time to remove.
Edit, Jan 2012
A worked example of how flexible this is: Need to calculate by rounded time or date figure in sql server
Edit, May 2012
Do not use this in WHERE clauses and the like without thinking: adding a function or CAST to a column invalidates index usage. See number 2 here Common SQL Programming Mistakes
Now, this does have an example of later SQL Server optimiser versions managing CAST to date correctly, but generally it will be a bad idea ...
Edit, Sep 2018, for datetime2
DECLARE #datetime2value datetime2 = '02180912 11:45' --this is deliberately within datetime2, year 0218
DECLARE #datetime2epoch datetime2 = '19000101'
select DATEADD(dd, DATEDIFF(dd, #datetime2epoch, #datetime2value), #datetime2epoch)
In SQL Server 2008, you can use:
CONVERT(DATE, getdate(), 101)
Of-course this is an old thread but to make it complete.
From SQL 2008 you can use DATE datatype so you can simply do:
SELECT CONVERT(DATE,GETDATE())
In SQL Server 2008, there is a DATE datetype (also a TIME datatype).
CAST(GetDate() as DATE)
or
declare #Dt as DATE = GetDate()
SELECT CAST(FLOOR(CAST(getdate() AS FLOAT)) AS DATETIME)
...is not a good solution, per the comments below.
I would delete this answer, but I'll leave it here as a counter-example since I think the commenters' explanation of why it's not a good idea is still useful.
Here's yet another answer, from another duplicate question:
SELECT CAST(CAST(getutcdate() - 0.50000004 AS int) AS datetime)
This magic number method performs slightly faster than the DATEADD method. (It looks like ~10%)
The CPU Time on several rounds of a million records:
DATEADD MAGIC FLOAT
500 453
453 360
375 375
406 360
But note that these numbers are possibly irrelevant because they are already VERY fast. Unless I had record sets of 100,000 or more, I couldn't even get the CPU Time to read above zero.
Considering the fact that DateAdd is meant for this purpose and is more robust, I'd say use DateAdd.
SELECT CAST(CAST(GETDATE() AS DATE) AS DATETIME)
I really like:
[date] = CONVERT(VARCHAR(10), GETDATE(), 120)
The 120 format code will coerce the date into the ISO 8601 standard:
'YYYY-MM-DD' or '2017-01-09'
Super easy to use in dplyr (R) and pandas (Python)!
BEWARE!
Method a) and b) does NOT always have the same output!
select DATEADD(dd, DATEDIFF(dd, 0, '2013-12-31 23:59:59.999'), 0)
Output: 2014-01-01 00:00:00.000
select cast(convert(char(11), '2013-12-31 23:59:59.999', 113) as datetime)
Output: 2013-12-31 00:00:00.000
(Tested on MS SQL Server 2005 and 2008 R2)
EDIT: According to Adam's comment, this cannot happen if you read the date value from the table, but it can happen if you provide your date value as a literal (example: as a parameter of a stored procedure called via ADO.NET).
See this question:
How can I truncate a datetime in SQL Server?
Whatever you do, don't use the string method. That's about the worst way you could do it.
Already answered but ill throw this out there too...
this suposedly also preforms well but it works by throwing away the decimal (which stores time) from the float and returning only whole part (which is date)
CAST(
FLOOR( CAST( GETDATE() AS FLOAT ) )
AS DATETIME
)
second time I found this solution... i grabbed this code off
CAST(round(cast(getdate()as real),0,1) AS datetime)
This method does not use string function. Date is basically a real datatype with digits before decimal are fraction of a day.
this I guess will be faster than a lot.
For me the code below is always a winner:
SELECT CONVERT(DATETIME, FLOOR(CONVERT(FLOAT,GETDATE())));
select CONVERT(char(10), GetDate(),126)
Strip time on inserts/updates in the first place. As for on-the-fly conversion, nothing can beat a user-defined function maintanability-wise:
select date_only(dd)
The implementation of date_only can be anything you like - now it's abstracted away and calling code is much much cleaner.
I think you mean
cast(floor(cast(getdate()as float))as datetime)
real is only 32-bits, and could lose some information
This is fastest
cast(cast(getdate()+x-0.5 as int)as datetime)
...though only about 10% faster(about 0.49 microseconds CPU vs. 0.58)
This was recommended, and takes the same time in my test just now:
DATEADD(dd, DATEDIFF(dd, 0, getdate()), 0)
In SQL 2008, the SQL CLR function is about 5 times faster than using a SQL function would be, at 1.35 microseconds versus 6.5 microsections, indicating much lower function-call overhead for a SQL CLR function versus a simple SQL UDF.
In SQL 2005, the SQL CLR function is 16 times faster, per my testing, versus this slow function:
create function dateonly ( #dt datetime )
returns datetime
as
begin
return cast(floor(cast(#dt as float))as int)
end
How about select cast(cast my_datetime_field as date) as datetime)? This results in the same date, with the time set to 00:00, but avoids any conversion to text and also avoids any explicit numeric rounding.
I think that if you stick strictly with TSQL that this is the fastest way to truncate the time:
select convert(datetime,convert(int,convert(float,[Modified])))
I found this truncation method to be about 5% faster than the DateAdd method. And this can be easily modified to round to the nearest day like this:
select convert(datetime,ROUND(convert(float,[Modified]),0))
Here I made a function to remove some parts of a datetime for SQL Server. Usage:
First param is the datetime to be stripped off.
Second param is a char:
s: rounds to seconds; removes milliseconds
m: rounds to minutes; removes seconds and milliseconds
h: rounds to hours; removes minutes, seconds and milliseconds.
d: rounds to days; removes hours, minutes, seconds and milliseconds.
Returns the new datetime
create function dbo.uf_RoundDateTime(#dt as datetime, #part as char)
returns datetime
as
begin
if CHARINDEX( #part, 'smhd',0) = 0 return #dt;
return cast(
Case #part
when 's' then convert(varchar(19), #dt, 126)
when 'm' then convert(varchar(17), #dt, 126) + '00'
when 'h' then convert(varchar(14), #dt, 126) + '00:00'
when 'd' then convert(varchar(14), #dt, 112)
end as datetime )
end
Just in case anyone is looking in here for a Sybase version since several of the versions above didn't work
CAST(CONVERT(DATE,GETDATE(),103) AS DATETIME)
Tested in I SQL v11 running on Adaptive Server 15.7
If possible, for special things like this, I like to use CLR functions.
In this case:
[Microsoft.SqlServer.Server.SqlFunction]
public static SqlDateTime DateOnly(SqlDateTime input)
{
if (!input.IsNull)
{
SqlDateTime dt = new SqlDateTime(input.Value.Year, input.Value.Month, input.Value.Day, 0, 0, 0);
return dt;
}
else
return SqlDateTime.Null;
}
I, personally, almost always use User Defined functions for this if dealing with SQL Server 2005 (or lower version), however, it should be noted that there are specific drawbacks to using UDF's, especially if applying them to WHERE clauses (see below and the comments on this answer for further details). If using SQL Server 2008 (or higher) - see below.
In fact, for most databases that I create, I add these UDF's in right near the start since I know there's a 99% chance I'm going to need them sooner or later.
I create one for "date only" & "time only" (although the "date only" one is by far the most used of the two).
Here's some links to a variety of date-related UDF's:
Essential SQL Server Date, Time and DateTime Functions
Get Date Only Function
That last link shows no less than 3 different ways to getting the date only part of a datetime field and mentions some pros and cons of each approach.
If using a UDF, it should be noted that you should try to avoid using the UDF as part of a WHERE clause in a query as this will greatly hinder performance of the query. The main reason for this is that using a UDF in a WHERE clause renders that clause as non-sargable, which means that SQL Server can no longer use an index with that clause in order to improve the speed of query execution. With reference to my own usage of UDF's, I'll frequently use the "raw" date column within the WHERE clause, but apply the UDF to the SELECTed column. In this way, the UDF is only applied to the filtered result-set and not every row of the table as part of the filter.
Of course, the absolute best approach for this is to use SQL Server 2008 (or higher) and separate out your dates and times, as the SQL Server database engine is then natively providing the individual date and time components, and can efficiently query these independently without the need for a UDF or other mechanism to extract either the date or time part from a composite datetime type.
I would use:
CAST
(
CAST(YEAR(DATEFIELD) as varchar(4)) + '/' CAST(MM(DATEFIELD) as varchar(2)) + '/' CAST(DD(DATEFIELD) as varchar(2)) as datetime
)
Thus effectively creating a new field from the date field you already have.