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The solution to our problem can be obtained using another built-in function – TIMESTAMPDIFF, which is similar to DATEDIFF function in SQL Server: We get one day even if the interval between dates is all one second: A positive result will be obtained if the first argument is greater than the second. Therefore, all three requests below will give the same result -1. In this case, if the date is presented in the date-time format, only the component of the date is used. DATEDIFF calculates the number of days between two dates that are arguments for this function. The DATEDIFF function is also present in MySQL, but it has a completely different meaning.
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The query uses the standard date representation (ISO) as a text string ‘yyyy-mm-ddThh:mm:ss’, which does not depend on either the local server settings or the server itself. The integrated DATEDIFF function solves the problem: Count the number of minutes between two dates – ‘ 23:43:00’ and ‘ 01:23:00’. For example, the number of days does not give us the number of hours divided by 24 (number of hours per day), but the number of jumps over midnight.
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Is that weird? Maybe, but as they say, whoever is warned is armed. If you keep that in mind, then an even more amazing example becomes clear: The fact is that the DATEDIFF function actually considers a week not the number of days, but the number of transitions from Saturday to Sunday. Now let’s take the interval from Saturday 29-10-2005 to Sunday 30-10-2005:
SQL SERVER DATEDIFF FULL
SELECT DATEDIFF(wk, '20051023', '20051029') Ĭommon sense suggests that this is a full week, but the above query gives 0. First we will count the number of weeks from Sunday 23-10-2005 to Saturday 29-10-2005. One thing to keep in mind is that the DATEDIFF function is used. The T-SQL DATEPART function can help here, which will be discussed in the next item. Now the second question: how do you calculate only the time, with whatever day it stands? So, if the time of arrival is not more than the time of departure, then this fact takes place. Secondly, it is unreliable to make any assumptions about a day that is present only because of the need to match the type of datetime.īut how do you know if the plane landed the next day? Here helps to describe the subject area, which says that the flight can not last more than 24 hours. (which gives 760 minutes) is wrong for two reasons.įirst, for flights that depart one day and arrive the next, the value calculated in this way will be incorrect SELECT DATEDIFF(mi, time_out, time_in) dur
SQL SERVER DATEDIFF UPDATE
That’s why if you insert only time into the datetime field (for example, UPDATE trip SET time_out = ’17:24:00′ WHERE trip_no = 1123), the time will be added with the default date value (), which is the starting point of time. As already mentioned, SQL Server up until version 2005 did not have separate temporal data types for date and time. Please note here that the departure time (time_out) and arrival time (time_in) are stored in the datetime fields of the Trip table type. The possible options are determined by the datepart argument and are listed above for the DATEADD function.ĭetermine the number of days that have passed between the first and last completed flight.ĭetermine the duration of flight 1123 in minutes. This interval can be measured in different units. The function returns the time interval between two time stamps – startdate and enddate.
SQL SERVER DATEDIFF HOW TO
Let’s look at some examples of the SQL Server function DATEDIFF to understand how to use the DATEDIFF function in SQL Server (Transact-SQL). SQL Server vNext, SQL Server 2016, SQL Server 2015, SQL Server 2014, SQL Server 2012, SQL Server 2008 R2, SQL Server 2008, SQL Server 2005 The DATEDIFF function can be used in future versions of SQL Server (Transact-SQL): This could be one of the following values: Meaning (any of)ĭate1, date2 – two dates to calculate the difference between them. Interval – time interval for calculating the difference between date1 and date2. Syntax of the DATEDIFF function in SQL Server (Transact-SQL)ĭATEDIFF( interval, date1, date2 ) Parameters or arguments