What does the number mean in this statement: DATEDIFF(wk, 6, '2020-01-03');

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The documentation states

DATEDIFF(interval, date1, date2);  

I can't find any info on what a number means there.

That would mean that the date is "6". If you run:

select convert(datetime,  6)

You will get a value.

More commonly, I think, it means that the write of the code intended DATEADD() rather than DATEDIFF().

SQL Server DATEDIFF Function By Practical Examples, In this tutorial, you will learn how to use SQL Server DATEDIFF() function to calculate the number of years, months, weeks, days,etc., between two dates. The MySQL DateDiff() function’s default return value is the number of days between two date or datetime expressions. And as we’ve also indicated earlier, if you run a query statement like this: Select datediff('2023-09-20','2023-09-15') as Difference;

I believe that the code

SELECT DATEDIFF(WK, 6 , '20200103')

Is actually starting from this date:

'1900-01-01 00:00:00.000'

The 6 is then adding 6 days to that date, making it the 7th of jan.

SELECT DATEDIFF(WK, '19000107', '20200103')

Running those 2 selects would output the same.

DateDiff function (Visual Basic for Applications), [ firstweekofyear ]] ). The DateDiff function syntax has these named arguments: vbFriday, 6, Friday If interval is Week ("ww"), however, the DateDiff function returns the number of calendar weeks between the two dates. Haroon's deep interest in logic and reasoning at an early age of his academic career paved his path to become a data professional. He began his professional life as a computer programmer more than 10 years ago working on his first data venture to migrate and rewrite a public sector database driven examination system from IBM AS400 (DB2) to SQL Server 2000 using VB 6.0 and Classic ASP along

That statement says, the week difference :

DATEDIFF(wk, 6, '2020-01-03')

6 would be 1900-01-07

So, you will get week difference for '1900-01-07' & '2020-01-03'

When you pass numeric value it will considered as no of days (being added in default date 1900-01-01)

For example, if you have a numeric value 1

select convert(datetime, 1)

You will get 1900-01-02 00:00:00.000, considering default date 1900-01-01

SQL date format Overview; DateDiff SQL function, DateAdd SQL , Note: It basically means that the input value is numeric; the SQL engine internally The SELECT statement selects the DATEPART, which is the function name, and it takes The number of dateparts separating two date/time instances is too large. DATEDIFF( week, @StartDate, @EndDate ) AS Weeks,. DATEDIFF for the WEEK datepart doesn't actually calculate weeks, it calculates the number of times a date range contains dates that represent pairs of Saturdays and Sundays. To think of it in more

The legacy datetime datatype is stored as two 32 bit integers concatenated together.

One integer is the offset in days from the base date of 1st Jan 1900, the other integer is the number of ticks for the time component.

Similarly SQL Server has long allowed casts between numeric types and datetime that correspond with this scheme. The integer 0 casts to Monday 1900-01-01, and 6 to Sunday 1900-01-07 for example.

When you call DATEDIFF and pass an integer as either of the last 2 parameters it gets implicitly cast to DATETIME so is the same as DATEDIFF(wk, {d '1900-01-07'}, date_under_test}.

Whilst the output of that expression is likely not interesting on its own it might be used to group values belonging to the same week (starting Sunday) together or combined with DATEADD to add this number of weeks plus one back on to the anchor date to get the following Sunday to date_under_test or similar.

DATEDIFF() Examples in SQL Server, In SQL Server, you can use the T-SQL DATEDIFF() function to return the difference between two dates/times. Here's a basic example where we find out the number of days between two dates: DATEDIFF( month, @date1, @date2 ) AS Months, DATEDIFF( week, Example 6 – Getting Weird Results? For example, you might use DateDiff to calculate the number of days between two dates, or the number of weeks between today and the end of the year. Behavior. Treatment of Parameters. DateDiff subtracts the value of Date1 from the value of Date2 to produce the difference. Neither value is changed in the calling program.

Example Uses of the DATEDIFF Date Function, The DATEDIFF date function returns the number of date and time bourndaries crossed DAY or DD or D, WEEK or WK or WW, WEEKDAY or DW or W, HOUR or HH, MINUTE or The <startdate> parameter is the starting date for the calculation and is an Usage #6 : Get Last Day of the Following Month, Quarter and Year DATEDIFF Case Statement - Calculate Number Of Days Feb 14, 2014 (I mean default computer date) Date” that if “System Date” is 45 days+ to “Due Date

MS Access: DateDiff Function, The Microsoft Access DateDiff function returns the difference between two date values, based on vbFriday, 6, Friday If this parameter is omitted, Access assumes that the week containing Jan 1st is the first week of the year. for DateDiff to Calculate between a due date and today and to show the number as a + not a -. The DATEDIFF function calculates the amount of time between two dates, where the time part is based on an interval of time, such as hours, days, weeks, months, years, etc. The DATEADD function calculates a date by taking an interval of time, and adding it to a date, where the interval of time will be the same as those used by the DATEDIFF function.

Date Manipulation with DATEADD/DATEDIFF – SQLServerCentral, Learn how to use Dateadd/Datediff functions to manipulate dates in this short There are a number of ways to accomplish this, but this article will focus on my For instance, you can sub out Days for Week, month or Year: As you'll recall, the INSERT statement (in the example that preceded this one) added a row with a DelivDate value of Sept. 6. However, the value is now Sept. 3, three days earlier. Using the DATEDIFF SQL Server function. The DATEDIFF function calculates the time interval between two dates and returns an integer that represents the interval.

Comments
  • Which dbms are you using? (DATEDIFF is not ANSI SQL.)
  • Syntax suggests SQL Server DB.
  • It means the person who wrote this code took some very tricky shortcuts. I'm sure you will find more of this unfortunately.