Oracle months_between function unexpected result - sql

Oracle's months_between function returns unexpected results.
For example, the difference between 20191001 and 20190916 is 15 days, so the return value of the function is expected to be (1/31) * 15 = 0.4838 ....
SELECT months_between('20191001','20190916')
from dual
.5161290322580645161290322580645161290323
Is this a specification? Or is it a bug?

The function MONTHS_BETWEEN works with 31 day months when the day-of-the-month is not the last day of the month.
SELECT MONTHS_BETWEEN
(TO_DATE('20190201','YYYYMMDD'),
TO_DATE('20190131','YYYYMMDD') ) "Months"
FROM DUAL;
will return 0.032 (rounded) but
SELECT MONTHS_BETWEEN
(TO_DATE('20190301','YYYYMMDD'),
TO_DATE('20190228','YYYYMMDD') ) "Months"
FROM DUAL;
will return 0.129
For a more complete description of MONTHS_BETWEN see the documentation

Here is a version for SQL Server which is accurate.
/***************************************************************************
Name : fsMonthsBetweenDates
Purpose : Mimics the Months_Between function in Oracle; except this one is 100% accurate
Author : Gordon de Rouyan
Date : 2022-09-24
***************************************************************************/
CREATE OR ALTER FUNCTION dbo.fsMonthsBetweenDates
(
#Date1 datetime,
#Date2 datetime,
#InclusiveFirstDay bit = 1
)
RETURNS numeric(10,5)
WITH SCHEMABINDING -- , INLINE = ON -- compatibility_level = 150
AS
BEGIN
-- Using all floats for numeric values
DECLARE #Months numeric(10,5) = 0;
IF #Date1 IS NOT NULL AND #Date2 IS NOT NULL
BEGIN
-- Include the first day or not; e.g. 2021-02-01 and 2021-02-01
-- Do you want to consider this combination as one day 2021-02-01#00:00:00 to 2021-02-01#23:59:59?
DECLARE #FirstDayInclusive int = CASE
WHEN #InclusiveFirstDayFlag = 1 THEN 1
ELSE 0
END;
-- Determine start date
DECLARE #StartDt date = CASE
WHEN CAST(#Date2 AS date) > CAST(#Date1 AS date) THEN #Date1
ELSE #Date2
END;
-- Determine end date
DECLARE #EndDt date = CASE
WHEN CAST(#Date2 AS date) > CAST(#Date1 AS date) THEN #Date2
ELSE #Date1
END;
DECLARE -- The DAY portion of the dates
#StartDtDay int = DAY(#StartDt),
#EndDtDay int = DAY(#EndDt),
-- Number of days in each month specific to each supplied date; exact with leap year
#StartDtMonthDays numeric(7,5) = DAY(EOMONTH(#StartDt)),
#EndDtMonthDays numeric(7,5) = DAY(EOMONTH(#EndDt));
DECLARE -- The fraction of the first month
#FirstMonthFraction numeric(6,5) = (#StartDtMonthDays - #StartDtDay + #FirstDayInclusive) / #StartDtMonthDays,
-- The fraction of the last month
#LastMonthFraction numeric(6,5) = #EndDtDay / #EndDtMonthDays;
SET #Months = DATEDIFF(MONTH, #StartDt, #EndDt) - 1 + (#FirstMonthFraction + #LastMonthFraction);
END;
RETURN #Months;
END;

Here is a version for SQL Server which mimics the same output as Oracle.
/***************************************************************************
Name : fsOracleMonths_Between
Purpose : Mimics the Months_Between function in Oracle; exactly the same values
Author : Gordon de Rouyan
Date : 2022-09-24
***************************************************************************/
CREATE OR ALTER FUNCTION [dbo].[fsOracleMonths_Between]
(
#Date1 datetime,
#Date2 datetime
)
RETURNS numeric(10,5)
WITH SCHEMABINDING -- , INLINE = ON -- SQL Server 2019, compatibility_level = 150
AS
BEGIN
DECLARE #Months numeric(10,5) = 0,
#OmbDate1 date = #Date1,
#OmbDate2 date = #Date2;
IF #Date1 IS NOT NULL AND #Date2 IS NOT NULL
AND #OmbDate1 <> #OmbDate2
BEGIN
-- Compare the datetime values
DECLARE #Date2GreaterThanDate1Flag bit = CASE
WHEN #OmbDate1 <= #OmbDate2 THEN 1
ELSE 0
END;
-- This ensures the correct value comes out based on the numeric(7,5)
-- int / numeric(7,5) = numeric(7,5)
-- numeric(7,5) / 31 = error
DECLARE #ConstantDay numeric(7,5) = 31;
-- The DAY portion of the dates
DECLARE #Date1Day int = DAY(#OmbDate1),
#Date2Day int = DAY(#OmbDate2);
-- Number of days in each month specific to each supplied date; exact with leap year
DECLARE #Date1MonthDays int = DAY(EOMONTH(#OmbDate1)),
#Date2MonthDays int = DAY(EOMONTH(#OmbDate2));
-- The fraction of the start month
DECLARE #StartMonthFraction numeric(6,5) = CASE
WHEN #Date2GreaterThanDate1Flag = 1 THEN (#ConstantDay - #Date1Day) / #ConstantDay
ELSE (#ConstantDay - #Date2Day) / #ConstantDay
END;
-- The fraction of the end month
DECLARE #EndMonthFraction numeric(6,5) = CASE
WHEN #Date2GreaterThanDate1Flag = 1 THEN #Date2Day / #ConstantDay
ELSE #Date1Day / #ConstantDay
END;
SET #Months = CASE
WHEN #Date2GreaterThanDate1Flag = 1 THEN DATEDIFF(MONTH, #OmbDate2, #OmbDate1 ) + 1 - (#StartMonthFraction + #EndMonthFraction)
ELSE DATEDIFF(MONTH, #OmbDate2, #OmbDate1) - 1 + (#StartMonthFraction + #EndMonthFraction)
END;
END;
RETURN #Months;
END;

Related

How to avoid not to query tables or views in scalar functions?

I have scalar functions( 4 functions) in my View. It drastically reduces the view's performance. I believe the reason for that is I use SELECT queries in my scalar functions.
EG:
CREATE FUNCTION [dbo].[udf_BJs_GENERAL]
(
#TankSystemId int,
#TimeStamp datetime2(7)
)
RETURNS varchar(10)
AS
BEGIN
DECLARE #leakChk varchar(10);
DECLARE #allowableVariance float;
DECLARE #GallonsPumped int;
DECLARE #DailyOverOrShort float;
DECLARE #TimePeriod datetime2(7);
DECLARE #ReportDate datetime2(7)
SELECT TOP 1 #TimePeriod = Date
FROM [bjs].udv_DailySiraData
where TankSystemId=#TankSystemId ORDER BY Date DESC
SET #ReportDate=#TimePeriod
IF( #TimeStamp <= #TimePeriod)
SET #ReportDate=#TimeStamp
SELECT #GallonsPumped = SUM(GallonsPumped)
FROM [bjs].[udv_DailySiraData]
where TankSystemId=#TankSystemId
and Date <=#ReportDate and Date >= DATEADD(mm, DATEDIFF(mm,0,#ReportDate), 0)
SELECT #DailyOverOrShort = SUM(DailyVar)
FROM [bjs].[udv_DailySiraData]
where TankSystemId=#TankSystemId
and Date <=#ReportDate and Date >= DATEADD(mm, DATEDIFF(mm,0,#ReportDate), 0)
SELECT #allowableVariance= (#GallonsPumped/100) + 130
SET #leakChk='FAIL'
IF (#allowableVariance > ABS(#DailyOverOrShort))
SET #leakChk = 'PASS'
RETURN #leakChk;
How can i avoid such situations? Is there a way to do select queries in my View and pass that result to my scalar function?
Try this:
create function dbo.udf_BJs_GENERAL(
#TankSystemId int,
#TimeStamp datetime2(7)
) returns varchar(10) as
with dates as (
select top 1
ReportDate = case when #TimeStamp <= Date then #TimeStamp else Date
from bjs.udv_DailySiraData
where TankSystemId=#TankSystemId
order by Date desc
),
gallons as (
select
allowableVariance = ( sum(GallonsPumped)/100) + 130,
DailyOverOrShort = sum(DailyVar)
from bjs.udv_DailySiraData data
join dates
on data.Date <= dates.ReportDate
and date.Date >= dateadd(mm, datediffmm, 0, dates.ReportDate), 0)
where TankSystemId = #TankSystemId
)
select
leakChk = cast( case when allowableVariance > ABS(DailyOverOrShort))
then 'PASS' else 'FAIL' end as varchar(10) )
from gallons
your case is special, your have a special input parameter,assue the timestamp parameter is on Day level
This view will return check result of each TankSystemId on every day.
Then join will your query with TankSystemId and Day.
But if the input parameter is more detail. I think it is difficult to convert this function to view
CREATE view [dbo].[uvw_BJs_GENERAL]
AS
BEGIN
/*
SET #ReportDate=#TimePeriod
IF( #TimeStamp <= #TimePeriod)
SET #ReportDate=#TimeStamp
*/
SELECT TankSystemId,b.[Date]
,GallonsPumped = SUM(GallonsPumped),DailyOverOrShort = SUM(DailyVar)
,leakChk=CASE WHEN (SUM(GallonsPumped)/100) + 130)> ABS(SUM(DailyVar)) THEN 'PASS' ELSE 'FAIL' END
FROM [bjs].[udv_DailySiraData] AS a
INNER JOIN (
SELECT CONVERT(DATE,[Date]) AS [Date] FROM [bjs].[udv_DailySiraData] GROUP BY TankSystemId, CONVERT(DATE,[Date])
) b ON a.TankSystemId=b.TankSystemId AND DATEDIFF(d,a.[Date],b.[Date])>=0
-- and Date <=#ReportDate and Date >= DATEADD(mm, DATEDIFF(mm,0,#ReportDate), 0)
GROUP BY TankSystemId,b.[Date]
END

How to add hours to work day in SQL?

I have seen many example adding working date (business days) to date in SQL. But I would like to add hour.
For example; I would like to add 36 hour to date not in Sunday , Saturday
Could one help me about it ?
CREATE FUNCTION AddWorkDays
(
#WorkingDays As Int,
#StartDate AS DateTime
)
RETURNS DateTime
AS
BEGIN
DECLARE #Count AS Int
DECLARE #i As Int
DECLARE #NewDate As DateTime
SET #Count = 0
SET #i = 0
WHILE (#i < #WorkingDays) --runs through the number of days to add
BEGIN
-- increments the count variable
SELECT #Count = #Count + 1
-- increments the i variable
SELECT #i = #i + 1
-- adds the count on to the StartDate and checks if this new date is a Saturday or Sunday
-- if it is a Saturday or Sunday it enters the nested while loop and increments the count variable
WHILE DATEPART(weekday,DATEADD(d, #Count, #StartDate)) IN (1,7)
BEGIN
SELECT #Count = #Count + 1
END
END
-- adds the eventual count on to the Start Date and returns the new date
SELECT #NewDate = DATEADD(d,#Count,#StartDate)
RETURN #NewDate
END
GO
The following will add N hours to a date (excluding Saturday and Sundays).
Example
Declare #Date1 datetime = '2017-04-28'
Declare #Hours int = 36
Select D=max(D)
From (
Select D,HN=-1+Row_Number() over (Order by D)
From (Select D=DateAdd(HOUR,-1+Row_Number() Over (Order By (select null)),#Date1) From master..spt_values n1 ) D
Where DateName(WEEKDAY,D) not in ('Saturday','Sunday')
) D1
Where HN=#Hours
Returns
2017-05-01 12:00:00.000
is it what you are looking for?
declare #num_hours int;
set #num_hours = 1;
select dateadd(HOUR, #num_hours, getdate()) as time_with_hour;
declare #num_hours int;
set #num_hours = 5;
select dateadd(HOUR, #num_hours, getdate()) as time_added,
getdate() as curr_date
This question is already answered Here

Calculating due date using business hours and holidays

I need to calculate due date / end date for SLAs. As input values I have the start date and a timespan (in minutes). This calculation needs to take into account business hours, weekends, and holidays.
I've seen a lot of examples where the input is start date and end date, but have been struggling finding anything similar to the above input values.
Is there an elegant solution to this problem? Is there a way to calculate due date without using a loop? I can't think of a way to do the calculation without doing something similar to the following terrible algorithm:
Create a return variable "due date" and set it to input variable
"start date"
Create a control variable "used minutes" and set it to 0
Create a loop with the condition "used minutes" <= "input timespan"
Inside the loop, add a second to the "due date" return variable
Inside the loop, check if the second is within hours of operation
(checking business hours, weekends, and holidays). If so, increment
control variable "used minutes" by 1.
Upon exiting the loop, return variable "due date"
You need a table with valid business hours, with the weekends and holidays excluded (or marked as weekend/holiday so you can skip them.) Each row represents one day and the number of working hours for that day. Then you query the business hours table from your start date to the first (min) date where the sum(hours*60) is greater than your minutes parameter, excluding marked weekend/holiday rows. That gives you your end date.
Here's the day table:
CREATE TABLE [dbo].[tblDay](
[dt] [datetime] NOT NULL,
[dayOfWk] [int] NULL,
[dayOfWkInMo] [int] NULL,
[isWeekend] [bit] NOT NULL,
[holidayID] [int] NULL,
[workingDayCount] [int] NULL,
CONSTRAINT [PK_tblDay] PRIMARY KEY CLUSTERED
(
[dt] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
here's how I populate the table with days:
CREATE PROCEDURE [dbo].[usp_tblDay]
AS
BEGIN
SET NOCOUNT ON;
DECLARE
#Dt datetime ,
#wkInMo int,
#firstDwOfMo int,
#holID int,
#workDayCount int,
#weekday int,
#month int,
#day int,
#isWkEnd bit
set #workDayCount = 0
SET #Dt = CONVERT( datetime, '2008-01-01' )
while #dt < '2020-01-01'
begin
delete from tblDay where dt = #dt
set #weekday = datepart( weekday, #Dt )
set #month = datepart(month,#dt)
set #day = datepart(day,#dt)
if #day = 1 -- 1st of mo
begin
set #wkInMo = 1
set #firstDwOfMo = #weekday
end
if ((#weekday = 7) or (#weekday = 1))
set #isWkEnd = 1
else
set #isWkEnd = 0
if #isWkEnd = 0 and (#month = 1 and #day = 1)
set #holID=1 -- new years on workday
else if #weekday= 6 and (#month = 12 and #day = 31)
set #holID=1 -- holiday on sat, change to fri
else if #weekday= 2 and (#month = 1 and #day = 2)
set #holID=1 -- holiday on sun, change to mon
else if #wkInMo = 3 and #weekday= 2 and #month = 1
set #holID = 2 -- mlk
else if #wkInMo = 3 and #weekday= 2 and #month = 2
set #holID = 3 -- President’s
else if #wkInMo = 4 and #weekday= 2 and #month = 5 and datepart(month,#dt+7) = 6
set #holID = 4 -- memorial on 4th mon, no 5th
else if #wkInMo = 5 and #weekday= 2 and #month = 5
set #holID = 4 -- memorial on 5th mon
else if #isWkEnd = 0 and (#month = 7 and #day = 4)
set #holID=5 -- July 4 on workday
else if #weekday= 6 and (#month = 7 and #day = 3)
set #holID=5 -- holiday on sat, change to fri
else if #weekday= 2 and (#month = 7 and #day = 5)
set #holID=5 -- holiday on sun, change to mon
else if #wkInMo = 1 and #weekday= 2 and #month = 9
set #holID = 6 -- Labor
else if #isWkEnd = 0 and (#month = 11 and #day = 11)
set #holID=7 -- Vets day on workday
else if #weekday= 6 and (#month = 11 and #day = 10)
set #holID=7 -- holiday on sat, change to fri
else if #weekday= 2 and (#month = 11 and #day = 12)
set #holID=7 -- holiday on sun, change to mon
else if #wkInMo = 4 and #weekday= 5 and #month = 11
set #holID = 8 -- thx
else if #holID = 8
set #holID = 9 -- dy after thx
else if #isWkEnd = 0 and (#month = 12 and #day = 25)
set #holID=10 -- xmas day on workday
else if #weekday= 6 and (#month = 12 and #day = 24)
set #holID=10 -- holiday on sat, change to fri
else if #weekday= 2 and (#month = 12 and #day = 26)
set #holID=10 -- holiday on sun, change to mon
else
set #holID = null
insert into tblDay select #dt,#weekday,#wkInMo,#isWkEnd,#holID,#workDayCount
if #isWkEnd=0 and #holID is null
set #workDayCount = #workDayCount + 1
set #dt = #dt + 1
if datepart( weekday, #Dt ) = #firstDwOfMo
set #wkInMo = #wkInMo + 1
end
END
I also have a holiday table, but everyone's holidays are different:
holidayID holiday rule description
1 New Year's Day Jan. 1
2 Martin Luther King Day third Mon. in Jan.
3 Presidents' Day third Mon. in Feb.
4 Memorial Day last Mon. in May
5 Independence Day 4-Jul
6 Labor Day first Mon. in Sept
7 Veterans' Day Nov. 11
8 Thanksgiving fourth Thurs. in Nov.
9 Fri after Thanksgiving Friday after Thanksgiving
10 Christmas Day Dec. 25
HTH
This is the best I could do, still uses a loop but uses date functions instead of incrementing a minutes variable. Hope you like it.
--set up our source data
declare #business_hours table
(
work_day varchar(10),
open_time varchar(8),
close_time varchar(8)
)
insert into #business_hours values ('Monday', '08:30:00', '17:00:00')
insert into #business_hours values ('Tuesday', '08:30:00', '17:00:00')
insert into #business_hours values ('Wednesday', '08:30:00', '17:00:00')
insert into #business_hours values ('Thursday', '08:30:00', '17:00:00')
insert into #business_hours values ('Friday', '08:30:00', '18:00:00')
insert into #business_hours values ('Saturday', '09:00:00', '14:00:00')
declare #holidays table
(
holiday varchar(10)
)
insert into #holidays values ('2015-01-01')
insert into #holidays values ('2015-01-02')
--Im going to assume the SLA of 2 standard business days (0900-1700) = 8*60*2 = 960
declare #start_date datetime = '2014-12-31 16:12:47'
declare #time_span int = 960-- time till due in minutes
declare #true bit = 'true'
declare #false bit = 'false'
declare #due_date datetime --our output
--other variables
declare #date_string varchar(10)
declare #today_closing datetime
declare #is_workday bit = #true
declare #is_holiday bit = #false
--Given our timespan is in minutes, lets also assume we dont care about seconds in start or due dates
set #start_date = DATEADD(ss,datepart(ss,#start_date)*-1,#start_date)
while (#time_span > 0)
begin
set #due_date = DATEADD(MINUTE,#time_span,#start_date)
set #date_string = FORMAT(DATEADD(dd, 0, DATEDIFF(dd, 0, #start_date)),'yyyy-MM-dd')
set #today_closing = (select convert(datetime,#date_string + ' ' + close_time) from #business_hours where work_day = DATENAME(weekday,#start_date))
if exists((select work_day from #business_hours where work_day = DATENAME(weekday,#start_date)))
set #is_workday = #true
else
set #is_workday = #false
if exists(select holiday from #holidays where holiday = #date_string)
set #is_holiday = #true
else
set #is_holiday = #false
if #is_workday = #true and #is_holiday = #false
begin
if #due_date > #today_closing
set #time_span = #time_span - datediff(MINUTE, #start_date, #today_closing)
else
set #time_span = #time_span - datediff(minute, #start_date, #due_date)
end
set #date_string = FORMAT(DATEADD(dd, 1, DATEDIFF(dd, 0, #start_date)),'yyyy-MM-dd')
set #start_date = CONVERT(datetime, #date_string + ' ' + isnull((select open_time from #business_hours where work_day = DATENAME(weekday,convert(datetime,#date_string))),''))
end
select #due_date
Sql to Calculate due date excluding holidays and considering business hour as below :- < note : - It's working correctly Business hour (8-5) Maintain holiday table
CREATE TABLE [dbo].[holiday](
[id] [int] IDENTITY(1,1) NOT NULL,
[region] [nvarchar](10) NULL,
[Hdate] [date] NULL,
)
>
declare #start datetime= getdate()
declare #slamins int =960 --- SLA time in mins
declare #Country varchar(2)='NA'
declare #start_hour int = 8 -- business start hour
declare #end_hour int = 17 -- business end hour
declare #true bit = 'true'
declare #false bit = 'false'
declare #is_workday bit = #true
declare #is_holiday bit = #false
declare #due_date datetime
declare #today_closing datetime
declare #temp int = 0
declare #holidays table (HDate DateTime) -- Table variable to hold holidayes
---- Get country holidays from table based on the country code (Feel free to remove this or modify as per your DB schema)
Insert Into #Holidays (HDate) Select date from HOLIDAY Where region=#Country and Hdate>=DateAdd(dd, DateDiff(dd,0,#start), 0)
--check for weekends
set #start = case(datepart(dw,#start)+##datefirst-1)%7
when 0 then Convert(dateTime,CONVERT(varchar,#start+1,101)+' 08:00:00')
when 6 then Convert(dateTime,CONVERT(varchar,#start+2,101)+' 08:00:00')
else #start end
-- check if start time is before business hour
if datepart(hh, #start) < #start_hour set #start = Convert(dateTime,CONVERT(varchar,#start,101)+' 08:00:00')
-- check if start time is after business hour
if datepart(hh, #start) >= #end_hour set #start = Convert(dateTime,CONVERT(varchar,#start+1,101)+' 08:00:00')
-- loop start
while (#slamins > 0)
begin
-- prepared closing date time based on start date
set #today_closing = Convert(dateTime,CONVERT(varchar,#start,101)+' 17:00:00')
set #due_date = #start
-- calculate number of Minute between start date and closing date
set #temp = DATEDIFF(N, #start , #today_closing);
--check for weekends
if (DATEPART(dw, #start)!=1 AND DATEPART(dw, #start)!=7)
set #is_workday = #true
else
set #is_workday = #false
--check for holidays
if (Select Count(*) From #Holidays Where HDATE=DateAdd(dd, DateDiff(dd,0,#start), 0)) = 0
set #is_holiday =#false
else
set #is_holiday = #true
if #is_workday = #true and #is_holiday = #false
begin
if(#temp < #slamins)
begin
set #slamins = #slamins - #temp
end
else
begin
set #due_date = DATEADD(MINUTE,#slamins,#start)
set #slamins = 0
print #due_date
end
end
set #start = Convert(dateTime,CONVERT(varchar,#start+1,101)+' 08:00:00')
end
select #due_date
Here is an option using a WorkSchedule table, which will contain the business hours that are available to count towards the SLA. To account for weekends and holidays, just do not insert records for these days into the WorkSchedule table.
This solution also uses a "Tally" table aka numbers table in the due date calc. I also included debug output to help you see what is going on, so just comment out or uncomment any debug sections to see less/more info.
I used SQL temp tables in this example so that you can run it without messing up your current database schema, but you should replace with physical tables if you use this solution.
Test Data setups:
CREATE TABLE #WorkSchedule(WorkStart datetime not null primary key, WorkEnd datetime not null);
GO
CREATE TABLE #Tally (N int not null primary key);
GO
--POPULATE TEST DATA
--populate Tally table
insert into #Tally (N)
select top 10000 N = row_number() over(order by o.object_id)
from sys.objects o cross apply sys.objects o2
;
go
--POPULATE WITH DUMMY TEST DATA
INSERT INTO #WorkSchedule(WorkStart, WorkEnd)
SELECT
workStart = dateadd(hour, 8, t.workDate)
, workEnd = dateadd(hour, 17, t.workDate)
FROM (
SELECT top 10000 workDate = dateadd(day, row_number() over(order by o.object_id), '2000-01-01')
FROM sys.objects o cross apply sys.objects o2
) t
--Exclude weekends from work schedule
WHERE datename(weekday, t.workDate) not in ('Saturday','Sunday')
;
GO
Code to calculate Due Date:
SET NOCOUNT ON;
DECLARE #startDate datetime;
DECLARE #SLA_timespan_mins int;
DECLARE #workStartDayOne datetime;
DECLARE #SLA_Adjusted int;
DECLARE #dueDate datetime;
--SET PARAM VALUES HERE FOR TESTING TO ANY DATE/SLA TIMESPAN YOU WANT:
SET #startDate = '2014-01-04 05:00'; --Saturday
SET #SLA_timespan_mins = 10 * 60 ; --10 hrs.
--get the info day 1, since your start date might be after the work start time.
select top 1 #workStartDayOne = s.WorkStart
--increase the SLA timespan mins to account for difference between work start and start time
, #SLA_Adjusted = case when #startDate > s.WorkStart then datediff(minute, s.WorkStart, #startDate) else 0 end + #SLA_timespan_mins
from #WorkSchedule s
where s.WorkEnd > #startDate
and s.WorkStart <> s.WorkEnd
order by s.WorkStart asc
;
--DEBUG info:
select 'Debug Info' as DebugInfo, #startDate AS StartDate, #workStartDayOne as workStartDayOne, #SLA_timespan_mins as SLA_timespan_mins, #SLA_Adjusted as SLA_Adjusted;
--now sum all the non work hours during that period and determine the additional mins that need added.
;with cteWorkMins as
(
SELECT TOP (#SLA_Adjusted)
s.WorkStart, s.WorkEnd
, WorkMinute = dateadd(minute, t.N, cast(s.WorkStart as datetime))
, t.N as MinuteOfWorkDay
, RowNum = row_number() over(order by s.WorkStart, t.N)
FROM #WorkSchedule s
INNER JOIN #Tally t
ON t.N between 1 and datediff(minute, s.WorkStart, s.WorkEnd)
WHERE s.WorkStart >= #workStartDayOne
ORDER BY s.WorkStart, t.N
)
/**/
SELECT #dueDate = m.WorkMinute
FROM cteWorkMins m
WHERE m.RowNum = #SLA_Adjusted
--*/
/**
--DEBUG: this query will show every minute that is accounted for during the Due Date calculation.
SELECT m.*
FROM cteWorkMins m
--WHERE m.RowNum = #SLA_Adjusted
ORDER BY m.WorkMinute
--*/
;
select #dueDate as DueDate;
GO
Test Cleanup:
IF object_id('TEMPDB..#WorkSchedule') IS NOT NULL
DROP TABLE #WorkSchedule;
GO
IF object_id('TEMPDB..#Tally') IS NOT NULL
DROP TABLE #Tally;
GO
as I understood from your question, what you need is as follow
You have given start date and number of minutes added to it, then you need to get the due date
To get the due date, you need to exclude the holidays and the due date should be during business day
here is what you can do
declare #start datetime,
#min int,
#days int
set #start= '28 Dec 2014'
set #min = 2200
-- get the number of days
set #days=datediff(day,#start,dateadd(minute,#min,#start))
-- get the due date
select max(Date)
from
(select row_number() over( order by t.Id)-1 as Id,t.Date
from DateMetadata t
inner join BusinessDays b on Day(t.Date) = b.Day
where t.Date > = #start and not exists(select 1 from Holidays h
where h.Day=Day(t.Date)
and h.Month=Month(t.Date))) as p
where p.Id < #days
Note :that DateMetadata table you will setup it in your database once
the setup for the above code :
create table Holidays(Id int identity(1,1),
Name nvarchar(50),
Day int,
Month int)
create table BusinessDays(Id int identity(1,1),
Name nvarchar(20),
Day int)
-- i am putting some days that are known,
-- it depends on you to define which holidays you want
insert into Holidays (Name,Day,Month) values('Christmas',25,12)
insert into Holidays(Name,Day,Month) values('New Year',31,12)
insert into Holidays(Name,Day,Month) values('Valentine',14,2)
insert into Holidays(Name,Day,Month) values('Mothers day',21,3)
insert into Holidays(Name,Day,Month) values('April fools day',1,4)
-- i am assuming that the business days are from monday till friday and
-- saturday and sunday are off days
insert into BusinessDays(Name,Day) values ('Monday',1)
insert into BusinessDays(Name,Day) values('Tuesday',2)
insert into BusinessDays(Name,Day) values('Wednesday',3)
insert into BusinessDays(Name,Day) values('Thursday',4)
insert into BusinessDays(Name,Day) values('Friday',5)
this table is needed and you will setup it once
-- set up a table that contains all dates from now till 2050 for example
-- and you can change the value of 2050 depending on your needs
-- this table you will setup it once
create table DateMetadata(Id int identity(1,1),
Date datetime)
declare #date datetime
set #date='01 Jan 2014'
while #date < '31 Dec 2050'
begin
insert into DateMetadata(Date) values(#date)
set #date = #date + 1
end
here a working DEMO
if you need any explanation, i am ready
hope it will help you
I created a function to calculate due date from the table, once it's populated as per Beth's and others' approaches (various similar methods for doing this, as you can see -- it only took me about an hour to think about all the UK holidays and populate the table including Easter dates up to 2029 without using these exact guides).
Note that my table contains SLA in business hours (8 hours in a normal day, 5 days in a normal week), your business hours may vary but you can amend this easily, just make sure your business hours are set the same for both the SLA table and the function below.
Code below is T-SQL (written in SSMS v17.8.1)
CREATE FUNCTION [JIRA].[Fn_JIRA_Due_Date] (
#CreatedDate DATETIME, #SLA_Business_Hours INTEGER
) RETURNS DATETIME
AS
-- SELECT [JIRA].[Fn_JIRA_Due_Date]('2019-12-28 08:00:00', 24)
/*
baldmosherâ„¢
2019-03-25
* Function returns the DueDate for a JIRA ticket, based on the CreatedDate and the SLA (based on the Issue Type, or the Epic for Tasks) and business hours per date (set in [JIRA].[Ref_JIRA_Business_Hours])
* Called by IUP to store this at the time the ticket is loaded
* Can only consider SLA in Business Hours:
* <24hrs calendar = <8hrs business
* =24hrs calendar = 8hrs business
* >24hrs calendar = 8hrs business * business days
*/
BEGIN
IF #CreatedDate IS NULL OR #SLA_Business_Hours IS NULL RETURN NULL;
DECLARE #SLA_Hours_Remaining SMALLINT = #SLA_Business_Hours;
--SET DATEFIRST 1;
DECLARE #DueDate DATETIME;
DECLARE #BusHrsStart DECIMAL(18,10) = 8 ; -- start of Business Hours (8am)
DECLARE #BusHrsClose DECIMAL(18,10) = 16 ; -- close of Business Hours (4pm)
--DECLARE #WkndStart DECIMAL(18,10) = 6 ; -- start of weekend (Sat)
DECLARE #Hours_Today SMALLINT ; -- # hours left in day to process ticket
-- PRINT 'Created ' + CAST(CAST(#CreatedDate AS DATE) AS VARCHAR(10)) + ' ' + CAST(CAST(#CreatedDate AS TIME) AS VARCHAR(8))
--!!!! extend to the next whole hour just to simplify reporting -- need to work on fixing this eventually
SET #CreatedDate = DATEADD(MINUTE,60-DATEPART(MINUTE,#CreatedDate),#CreatedDate)
-- PRINT 'Rounded ' + CAST(CAST(#CreatedDate AS DATE) AS VARCHAR(10)) + ' ' + CAST(CAST(#CreatedDate AS TIME) AS VARCHAR(8))
--check if created outside business hours and adjust CreatedDate to start the clock first thing at the next business hours start of day (days are checked next)
IF DATEPART(HOUR,#CreatedDate) < #BusHrsStart
--created before normal hours, adjust #CreatedDate later to #BusHrsStart same day
BEGIN
SET #CreatedDate = DATEADD(HOUR,#BusHrsStart,CAST(CAST(#CreatedDate AS DATE) AS DATETIME))
END
IF DATEPART(HOUR,#CreatedDate) >= #BusHrsClose
--created after normal hours, adjust #CreatedDate to #BusHrsStart next day
BEGIN
SET #CreatedDate = DATEADD(HOUR,#BusHrsStart,CAST(CAST(#CreatedDate+1 AS DATE) AS DATETIME))
--adjust CreatedDate to start the clock the next day with >0 business hours (i.e. extend if it falls on a weekend or holiday)
SET #CreatedDate = CAST(#CreatedDate AS DATE)
StartNextWorkingDay:
IF (SELECT TOP(1) [Business_Hours] FROM [JIRA].[Ref_JIRA_Business_Hours] b WHERE b.[Date] = #CreatedDate ORDER BY [Date]) = 0
BEGIN
SET #CreatedDate = DATEADD(DAY,1,#CreatedDate)
GOTO StartNextWorkingDay
END
--DATEADD(DAY, DATEDIFF(DAY,0,#CreatedDate+7)/7*7,0); -- midnight, Monday next week
SET #CreatedDate = DATEADD(HOUR,#BusHrsStart,#CreatedDate); -- BusHrsStart
END
-- PRINT 'Started ' + CAST(CAST(#CreatedDate AS DATE) AS VARCHAR(10)) + ' ' + CAST(CAST(#CreatedDate AS TIME) AS VARCHAR(8))
--third, check the business hours for each date from CreatedDate onwards to determine the relevant DueDate
SET #DueDate = #CreatedDate
-- PRINT 'SLA Hrs ' + CAST(#SLA_Hours_Remaining AS VARCHAR(2))
SET #Hours_Today = #BusHrsStart + (SELECT TOP(1) [Business_Hours] FROM [JIRA].[Ref_JIRA_Business_Hours] b WHERE b.[Date] = CAST(#DueDate AS DATE) ORDER BY [Date]) - DATEPART(HOUR, #CreatedDate)
-- PRINT 'Hrs Today ' + CAST(#Hours_Today AS VARCHAR(2))
DueNextWorkingDay:
IF #SLA_Hours_Remaining > #Hours_Today
BEGIN
-- PRINT 'Due another day'
SET #SLA_Hours_Remaining = #SLA_Hours_Remaining - #Hours_Today --adjust remaining time after today's hours
SET #Hours_Today = (SELECT TOP(1) [Business_Hours] FROM [JIRA].[Ref_JIRA_Business_Hours] b WHERE b.[Date] = CAST(#DueDate AS DATE) ORDER BY [Date])
-- PRINT 'SLA Hrs ' + CAST(#SLA_Hours_Remaining AS VARCHAR(2))
-- PRINT 'Hrs Today ' + CAST(#Hours_Today AS VARCHAR(2))
SET #DueDate = DATEADD(DAY,1,DATEADD(HOUR,#BusHrsStart,CAST(CAST(#DueDate AS DATE) AS DATETIME))) --adjust DueDate to first thing next day
END
IF #SLA_Hours_Remaining <= #Hours_Today
BEGIN
-- PRINT 'Due today'
SET #DueDate = DATEADD(HOUR,#SLA_Hours_Remaining,#DueDate)
END
ELSE
BEGIN
GOTO DueNextWorkingDay
END
-- PRINT 'DueDate ' + CAST(CAST(#DueDate AS DATE) AS VARCHAR(10)) + ' ' + CAST(CAST(#DueDate AS TIME) AS VARCHAR(8))
RETURN #DueDate
END
GO
Table for SLAs:
CREATE TABLE [JIRA].[Ref_JIRA_SLAs](
[SLA_SK] [SMALLINT] IDENTITY(1,1) NOT NULL,
[Project] [VARCHAR](20) NULL,
[Issue_Type] [VARCHAR](50) NULL,
[Epic_Name] [VARCHAR](50) NULL,
[SLA_Business_Hours] [SMALLINT] NULL,
[Comments] [VARCHAR](8000) NULL
) ON [PRIMARY] WITH (DATA_COMPRESSION = PAGE)
GO

SQL Nth Day of Nth Week of a Month

I want to use the following function for scheduling club meetings which occur on a monthly basis based on the week and weekday of the month. In the example below I have a (to be) function that returns the Third Wednesday of the month. If that day occurs in the past then it returns the next month's 3rd Wednesday.
I want to get away from the Loops and I feel that there is a better method for calculation. Is there a more OO process? Your opinion?
--CREATE FUNCTION NextWeekDayofMonth
DECLARE
--(
#WEEK INT,
#WEEKDAY INT,
#REFERENCEDATE DATETIME
--)
--RETURNS DATETIME
--AS
-------------------------------
--Values for testing - Third Wednesday of the Month
set #WEEK = 3 --Third Week
set #WEEKDAY = 4 --Wednesday
set #REFERENCEDATE = '08/20/2011'
-------------------------------
BEGIN
DECLARE #WEEKSEARCH INT
DECLARE #FDOM DATETIME
DECLARE #RETURNDATE DATETIME
SET #FDOM = DATEADD(M,DATEDIFF(M,0,#REFERENCEDATE),0)
SET #RETURNDATE = DATEADD(M,0,#FDOM)
WHILE (#RETURNDATE < #REFERENCEDATE)
--If the calculated date occurs in the past then it
--finds the appropriate date in the next month
BEGIN
SET #WEEKSEARCH = 1
SET #RETURNDATE = #FDOM
--Finds the first weekday of the month that matches the provided weekday value
WHILE ( DATEPART(DW,#RETURNDATE) <> #WEEKDAY)
BEGIN
SET #RETURNDATE = DATEADD(D,1,#RETURNDATE)
END
--Iterates through the weeks without going into next month
WHILE #WEEKSEARCH < #WEEK
BEGIN
IF MONTH(DATEADD(WK,1,#RETURNDATE)) = MONTH(#FDOM)
BEGIN
SET #RETURNDATE = DATEADD(WK,1,#RETURNDATE)
SET #WEEKSEARCH = #WEEKSEARCH+1
END
ELSE
BREAK
END
SET #FDOM = DATEADD(M,1,#FDOM)
END
--RETURN #RETURNDATE
select #ReturnDate
END
IMO, the best process is to store important business information as rows in tables in a database. If you build a calendar table, you can get all the third Wednesdays by a simple query. Not only are the queries simple, they can be seen to be obviously correct.
select cal_date
from calendar
where day_of_week_ordinal = 3
and day_of_week = 'Wed';
The third Wednesday that's on or after today is also simple.
select min(cal_date)
from calendar
where day_of_week_ordinal = 3
and day_of_week = 'Wed'
and cal_date >= CURRENT_DATE;
Creating a calendar table is straightforward. This was written for PostgreSQL, but it's entirely standard SQL (I think) except for the columns relating to ISO years and ISO weeks.
create table calendar (
cal_date date primary key,
year_of_date integer not null
check (year_of_date = extract(year from cal_date)),
month_of_year integer not null
check (month_of_year = extract(month from cal_date)),
day_of_month integer not null
check (day_of_month = extract(day from cal_date)),
day_of_week char(3) not null
check (day_of_week =
case when extract(dow from cal_date) = 0 then 'Sun'
when extract(dow from cal_date) = 1 then 'Mon'
when extract(dow from cal_date) = 2 then 'Tue'
when extract(dow from cal_date) = 3 then 'Wed'
when extract(dow from cal_date) = 4 then 'Thu'
when extract(dow from cal_date) = 5 then 'Fri'
when extract(dow from cal_date) = 6 then 'Sat'
end),
day_of_week_ordinal integer not null
check (day_of_week_ordinal =
case
when day_of_month >= 1 and day_of_month <= 7 then 1
when day_of_month >= 8 and day_of_month <= 14 then 2
when day_of_month >= 15 and day_of_month <= 21 then 3
when day_of_month >= 22 and day_of_month <= 28 then 4
else 5
end),
iso_year integer not null
check (iso_year = extract(isoyear from cal_date)),
iso_week integer not null
check (iso_week = extract(week from cal_date))
);
You can populate that table with a spreadsheet or with a UDF. Spreadsheets usually have pretty good date and time functions. I have a UDF, but it's written for PostgreSQL (PL/PGSQL), so I'm not sure how much it would help you. But I'll post it later if you like.
Here's a date math way to accomplish what you want without looping:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Description: Gets the nth occurrence of a given weekday in the month containing the specified date.
-- For #dayOfWeek, 1 = Sunday, 2 = Monday, 3 = Tuesday, 4 = Wednesday, 5 = Thursday, 6 = Friday, 7 = Saturday
-- =============================================
CREATE FUNCTION GetWeekdayInMonth
(
#date datetime,
#dayOfWeek int,
#nthWeekdayInMonth int
)
RETURNS datetime
AS
BEGIN
DECLARE #beginMonth datetime
DECLARE #offSet int
DECLARE #firstWeekdayOfMonth datetime
DECLARE #result datetime
SET #beginMonth = DATEADD(DAY, -DATEPART(DAY, #date) + 1, #date)
SET #offSet = #dayOfWeek - DATEPART(dw, #beginMonth)
IF (#offSet < 0)
BEGIN
SET #firstWeekdayOfMonth = DATEADD(d, 7 + #offSet, #beginMonth)
END
ELSE
BEGIN
SET #firstWeekdayOfMonth = DATEADD(d, #offSet, #beginMonth)
END
SET #result = DATEADD(WEEK, #nthWeekdayInMonth - 1, #firstWeekdayOfMonth)
IF (NOT(MONTH(#beginMonth) = MONTH(#result)))
BEGIN
SET #result = NULL
END
RETURN #result
END
GO
DECLARE #nextMeetingDate datetime
SET #nextMeetingDate = dbo.GetWeekdayInMonth(GETDATE(), 4, 3)
IF (#nextMeetingDate IS NULL OR #nextMeetingDate < GETDATE())
BEGIN
SET #nextMeetingDate = dbo.GetWeekDayInMonth(DATEADD(MONTH, 1, GETDATE()), 4, 3)
END
SELECT #nextMeetingDate
Here's another function based solution using date math that returns the Next Nth Weekday on or after a given date. It doesn't use any looping to speak of, but it may recurs by at most one iteration if the next Nth weekday is in the next month.
This function takes the DATEFIRST setting into account for environments that use a value other than the default.
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: David Grimberg
-- Create date: 2015-06-18
-- Description: Gets the next Nth weekday
-- #param Date is any date in a month
-- #param DayOfWeek is the weekday of interest ranging
-- from 1 to 7 with ##DATEFIRST being the
-- first day of the week
-- #param NthWeekday represents which ordinal weekday to return.
-- Positive values return dates relative to the start
-- of the month. Negative values return dates relative
-- to the end of the month. Values > 4 indicate the
-- last week, values < -4 indicate the first week.
-- Zero is assumed to be 1.
-- =============================================
ALTER FUNCTION dbo.xxGetNextNthWeekday
(
#Date date,
#NthWeekday smallint,
#DayOfWeek tinyint
)
RETURNS date
AS
BEGIN
DECLARE #FirstOfMonth date
DECLARE #inc int
DECLARE #Result date
-- Clamp the #NthWeekday input to valid values
set #NthWeekday = case when #NthWeekday = 0 then 1
when #NthWeekday > 4 then -1
when #NthWeekday < -4 then 1
else #NthWeekday
end
-- Normalize the requested day of week taking
-- ##DATEFIRST into consideration.
set #DayOfWeek = (##DATEFIRST + 6 + #DayOfWeek) % 7 + 1
-- Gets the first of the current month or the
-- next month if #NthWeekday is negative.
set #FirstOfMonth = dateadd(month, datediff(month,0,#Date)
+ case when #NthWeekday < 0 then 1 else 0 end
, 0)
-- Add and/or subtract 1 week depending direction of search and the
-- relationship of #FirstOfMonth's Day of the Week to the #DayOfWeek
-- of interest
set #inc = case when (datepart(WEEKDAY, #FirstOfMonth)+##DATEFIRST-1)%7+1 > #DayOfWeek
then 0
else -1
end
+ case when #NthWeekday < 0 then 1 else 0 end
-- Put it all together
set #Result = dateadd( day
, #DayOfWeek-1
, dateadd( WEEK
, #NthWeekday + #inc
, dateadd( WEEK -- Gets 1st Sunday on or
, datediff(WEEK, -1, #FirstOfMonth)
,-1 ) ) ) -- before #FirstOfMonth
-- [Snip here] --
if #Result < #Date
set #Result = dbo.xxGetNextNthWeekday( dateadd(month, datediff(month, 0, #Date)+1, 0)
, #NthWeekday, #DayOfWeek)
-- [to here for no recursion] --
Return #Result
END
If you want the past or future Nth weekday of the current month based on the #Date parameter rather than the next Nth weekday snip out the recursive part as indicated above.

How can I convert a week (200851) into a date (2008-12-27)?

How could I convert a year-week (for example, 0852 or 200852) into a date (for example, 2008-12-31 or specifically a week-ending day, that is, Saturday 2008-12-27 or a week-beginning day, that is, 2008-12-21)?
Any day of the week-ending will do, Friday, Saturday, Sunday or Monday.
SQL Server has the DATEADD functionality that should help...
DECLARE #date_string NCHAR(6)
SELECT #date_string = N'200852'
SELECT DATEADD(
WEEK,
CAST(RIGHT(#date_string, 2) AS INT),
DATEADD(
YEAR,
CAST(LEFT(#date_string, 4) AS INT) - 1900,
0
)
)
Once you have the value, use DATEPART to get what day of the week it is, and subtract that from your answer...
DECLARE #new_date DATETIME
SELECT #new_date = '2008 Dec 30'
SELECT DATEADD(DAY, 1-DATEPART(dw, #new_date), #new_date)
This will bring the value to the start of the week, depending on what you have set DATEFIRST to.
I've created a UDF for this purpose.
It'll convert a YYYYWW string or number to a date.
CREATE FUNCTION dbo.GetDateFromYearWeek (
#YearWeek VARCHAR(7) = '000101', -- default
#WeekDay INT = 1, -- default
#FirstWeekDayName VARCHAR(9) = 'mon' -- default
) RETURNS DATE
BEGIN
IF #YearWeek = '000101'
SET #YearWeek = CONCAT(DATEPART(year, GETDATE()), '-', DATEPART(week, GETDATE()));
IF #YearWeek NOT LIKE '[0-9][0-9][0-9][0-9]%[0-9-][0-9]'
RETURN NULL;
IF #WeekDay < 1 OR #WeekDay > 7
RETURN NULL;
DECLARE #FirstWeekDay INT = CHARINDEX(LOWER(LEFT(#FirstWeekDayName,3)), ' montuewedthufrisatsun')/3;
IF #FirstWeekDay = 0 -- not found in string
SET #FirstWeekDay = ##DATEFIRST;
DECLARE #Year INT = TRY_CAST(LEFT(#YearWeek, 4) AS INT);
DECLARE #Week INT = ABS(TRY_CAST(RIGHT(#YearWeek, 2) AS INT));
DECLARE #Date DATE = TRY_CAST(CONCAT(#Year,'-01-01') AS DATE);
SET #Date = DATEADD(week, #Week-1, #Date);
DECLARE #DowDiff INT = (6-#FirstWeekday+##DATEFIRST+DATEPART(weekday,#Date))%7;
SET #Date = DATEADD(day, -#DowDiff, #Date);
SET #Date = DATEADD(day, #WeekDay-1, #Date);
RETURN #Date;
END;
Example usage:
SELECT *
, [StartOfWeek_SundayFirst] = dbo.GetDateFromYearWeek(col, 1, 'sun')
, [StartOfWeek_MondayFirst] = dbo.GetDateFromYearWeek(col, 1, 'mon')
, [EndOfWeek_SundayFirst] = dbo.GetDateFromYearWeek(col, 7, 'sunday')
, [EndOfWeek_MondayFirst] = dbo.GetDateFromYearWeek(col, 7, 'monday')
FROM (VALUES (202201), (202202)) q(col)
ORDER BY 1;
col
StartOfWeek_SundayFirst
StartOfWeek_MondayFirst
EndOfWeek_SundayFirst
EndOfWeek_MondayFirst
202201
2021-12-26
2021-12-27
2022-01-01
2022-01-02
202202
2022-01-02
2022-01-03
2022-01-08
2022-01-09
Test it on the db<>fiddle here.
ISO_WEEK Version
CREATE FUNCTION dbo.GetDateFromIsoYearWeek (
#YearWeek VARCHAR(7) = '0000-00', -- default
#WeekDay INT = 1 -- default
) RETURNS DATE
BEGIN
IF #YearWeek = '0000-00'
SET #YearWeek = CONCAT(DATEPART(year, GETDATE()), '-', DATEPART(iso_week, GETDATE()));
IF #YearWeek NOT LIKE '[0-9][0-9][0-9][0-9]%[0-9-][0-9]'
RETURN NULL;
IF #WeekDay < 1 OR #WeekDay > 7
RETURN NULL;
DECLARE #FirstWeekDay INT = 1; -- monday
DECLARE #Year INT = TRY_CAST(LEFT(#YearWeek, 4) AS INT);
DECLARE #Week INT = ABS(TRY_CAST(RIGHT(#YearWeek, 2) AS INT));
DECLARE #Date DATE = TRY_CAST(CONCAT(#Year,'-01-08') AS DATE);
SET #Date = DATEADD(week, #Week - 2 + (DATEPART(week, #Date)-(DATEPART(iso_week, #Date))), #Date);
DECLARE #DowDiff INT = (6-#FirstWeekday+##DATEFIRST+DATEPART(weekday,#Date))%7;
SET #Date = DATEADD(day, -#DowDiff, #Date);
SET #Date = DATEADD(day, #WeekDay-1, #Date);
RETURN #Date;
END;
DECLARE #Test TABLE ([column] char(7));
INSERT INTO #Test VALUES
('2020-53'), ('2021-01'), ('2021-02')
, ('2021-48')
, ('2021-53'), ('2022-01'), ('2022-02')
;
SELECT [column]
, [FirstOfWeek] = dbo.GetDateFromIsoYearWeek([column], 1)
, [LastOfWeek] = dbo.GetDateFromIsoYearWeek([column], 7)
FROM #Test
ORDER BY 1;
column
FirstOfWeek
LastOfWeek
2020-53
2020-12-28
2021-01-03
2021-01
2021-01-04
2021-01-10
2021-02
2021-01-11
2021-01-17
2021-48
2021-11-29
2021-12-05
2021-53
2022-01-03
2022-01-09
2022-01
2022-01-03
2022-01-09
2022-02
2022-01-10
2022-01-16
Test it on the db<>fiddle here.
Here's a solution that's almost database independent, if that's important.
Create a table called ALMANAC, primary key DATE, that lists all the attributes of a date that you plan on using. One of them could be YEAR, another could be WEEK. You can include whatever computable functions of DATE you want to use a lot. You could also include company specific DATE attributes, like whether the date is a company holiday.
Write one program to populate DATE for say 10 years (about 3650 rows plus some leap years). This program will use the environment specific date functions available to you either in the DBMS of in some programming language. Once you've populated the ALMANAC table, use it like ordinary data. Join the primary key with any Date fields in your database.
This turns out to be enormously useful for doing such things as preparing a report by week, by month, by quarter, and by year, almost automatically.
If DATE isn't fine enough granularity, you can even divide the Almanac into smaller units of time, like shifts where 3 shifts is one day.
Date functions are pretty much database-specific. In MySQL, for example, you could do the following to get the Monday of the week in 'YYYYWW' format:
select date_sub(makedate(left('YYYYWW', 4), 1 + (right('YYYYWW', 2) - 1) * 7),
interval weekday(makedate(left('YYYYWW', 4), 1 + (right('YYYYWW', 2) - 1) * 7)) DAY);
With makedate(left('YYYYWW', 4), 1 + (right('YYYYWW', 2) - 1) * 7) you would get a date which is definitely in the given week and year, and with the date_sub function we go back to the Monday of that week.
Examples:
for '200906' this would return '2009-02-02
for '200901' it would return '2008-12-29' (this is in fact the Monday of week 1 of 2009)
In Oracle:
SELECT TO_DATE('04.01.' || SUBSTR(iso, 1, 4)) + (TO_NUMBER(SUBSTR(iso, 5, 2))) * 7 - TO_CHAR(TO_DATE('04.01.' || SUBSTR(iso, 1, 4)), 'D')
FROM (
SELECT '200101' AS iso
FROM dual
)
If this is in Oracle, check out the TO_Date function with various options, for example, "YYYYWW":
select TO_Date ('200852' YYYYWW) from dual;
Ref.: Oracle date format
Once you get the beginning of the week, you can always add the number of days to get the weekend date.