CODEWITHSUNDEEP
sqlt-sqldatesql-server-2016
Branco
Branco

Reputation: 201

Finding specific day in month SQL

I am trying to find a specific days within specific months for DST settings. I found code from another post. 

SELECT
DATEADD(day,DATEDIFF(day,'19000107',DATEADD(month,DATEDIFF(MONTH,0,GETDATE()/*YourValuehere*/),30))/7*7,'19000107')

I also found this in another post which could be used a month ahead.

SELECT DATEADD(day,-1 - (DATEPART(weekday, @StartOfMarch) + @@DATEFIRST - 2) % 7,
           @StartOfMarch
          ) AS LastSunday

I am not great with SQL so I am looking for a dummy explanation of what is happening here, and why this code works. From what I gather, Jan 07 1900 is significant in here as is the various built in date time functions. A simple play-by-play breakdown would help me understand what all is happening.

This is for the SQL Server 2016.

Upvotes: 1

Views: 2504

Answers (3)

Praveen Jayapal
Praveen Jayapal

Reputation: 73

You can try as below

SELECT * FROM <TABLE> WHERE DAY(<DATEFIELD>)=3 AND MONTH(<DATEFIELD>)=12

This will get me the entire list which falls in 3rd of every December.

Upvotes: 0

Zohar Peled
Zohar Peled

Reputation: 82474

Well, since 2012 version there is a built in function to get the end of the month for any date / datetime value called EOMONTH.
Using this function with DATEPART and DATEADD is quite a simple way to get the date of the last sunday in any given month:

DECLARE @Date datetime = GETDATE();
SELECT DATEADD(DAY, 1-DATEPART(WEEKDAY, EOMONTH(@Date)), EOMONTH(@Date)) As LastSundayDate

Result: 

LastSundayDate
30.04.2017 00:00:00

Another example:

SET @Date = DATEADD(MONTH, -1, GETDATE());
SELECT DATEADD(DAY, 1-DATEPART(WEEKDAY, EOMONTH(@Date)), EOMONTH(@Date)) As LastSundayDate;

Result: 

LastSundayDate
26.03.2017 00:00:00

Update

As SqlZim wrote in his comment, this relies on setting the first day of the month at sunday (using set datefirst 7; before using this query.

Upvotes: 2

John Cappelletti
John Cappelletti

Reputation: 81930

If you are interested, I'll often use a Table-Valued-Function to create dynamic date/time ranges. A tally/calendar table would do the trick as well. However, with a UDF, you can supply Date/Time Range, DatePart and Increment.

Also, being a TVF, it is easy to incorporate into a Sub-Query, Cross Join, etc.

In your case, if you are looking for the last Sunday in March and October

Example

Select D=Max(RetVal) 
 From [dbo].[udf-Range-Date]('2017-01-01','2017-12-31','DD',1)
 Where DateName(WEEKDAY,RetVal) = 'Sunday'
   and DatePart(MONTH,RetVal) in (3,11)
 Group By Year(RetVal),Month(RetVal)

Returns

D
2017-03-26
2017-11-26

The UDF if Interested

CREATE FUNCTION [dbo].[udf-Range-Date] (@R1 datetime,@R2 datetime,@Part varchar(10),@Incr int)
Returns Table
Return (
    with cte0(M)   As (Select 1+Case @Part When 'YY' then DateDiff(YY,@R1,@R2)/@Incr When 'QQ' then DateDiff(QQ,@R1,@R2)/@Incr When 'MM' then DateDiff(MM,@R1,@R2)/@Incr When 'WK' then DateDiff(WK,@R1,@R2)/@Incr When 'DD' then DateDiff(DD,@R1,@R2)/@Incr When 'HH' then DateDiff(HH,@R1,@R2)/@Incr When 'MI' then DateDiff(MI,@R1,@R2)/@Incr When 'SS' then DateDiff(SS,@R1,@R2)/@Incr End),
         cte1(N)   As (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
         cte2(N)   As (Select Top (Select M from cte0) Row_Number() over (Order By (Select NULL)) From cte1 a, cte1 b, cte1 c, cte1 d, cte1 e, cte1 f, cte1 g, cte1 h ),
         cte3(N,D) As (Select 0,@R1 Union All Select N,Case @Part When 'YY' then DateAdd(YY, N*@Incr, @R1) When 'QQ' then DateAdd(QQ, N*@Incr, @R1) When 'MM' then DateAdd(MM, N*@Incr, @R1) When 'WK' then DateAdd(WK, N*@Incr, @R1) When 'DD' then DateAdd(DD, N*@Incr, @R1) When 'HH' then DateAdd(HH, N*@Incr, @R1) When 'MI' then DateAdd(MI, N*@Incr, @R1) When 'SS' then DateAdd(SS, N*@Incr, @R1) End From cte2 )

    Select RetSeq = N+1
          ,RetVal = D 
     From  cte3,cte0 
     Where D<=@R2
)
/*
Max 100 million observations -- Date Parts YY QQ MM WK DD HH MI SS
Syntax:
Select * from [dbo].[udf-Range-Date]('2016-10-01','2020-10-01','YY',1) 
Select * from [dbo].[udf-Range-Date]('2016-01-01','2017-01-01','MM',1) 
*/

Upvotes: 2

Related Questions