Produce output of previous year and month correctly - sql

This sql was created to check the date but when I run a test for 2 month ago the output is 201700 and not 201612.
DECLARE #PeriodID AS CHAR(6)
SELECT #PeriodID = CONVERT(char(4), YEAR(GETDATE())) +
CASE
WHEN MONTH(GETDATE())<10 THEN '0' +CONVERT(char(2),MONTH(GETDATE())-2)
ELSE CONVERT(char(2),MONTH(GETDATE())-1)
END
print #periodid


I agree with Tim's answer, however the code he wrote is a bit combersome.
The following code should provide the same result, using only one DateAdd and one Convert:
DECLARE #PeriodID AS CHAR(6)
SELECT #PeriodID = CONVERT(CHAR(6), DATEADD(MONTH, -2, GETDATE()), 112)
PRINT #PeriodID
Results (for today - 2017-02-02):
201612


I think the simplest way to handle this is just to compute the date for 2 months ago, and then format the output with only the year and month, as your question implies:
SELECT CONVERT(CHAR(4), YEAR(DATEADD(month, -2, GETDATE()))) +
RIGHT('00' + CAST(MONTH(DATEADD(month, -2, GETDATE())) AS CHAR(2)), 2) AS periodId
FROM yourTable

Related

T-SQL How to get Week Number (ISO) of First Week from all Quarters from GetDate()?

The title says it pritty much.
But to be more precise, I need to get the Week Number of each week first starting in Quarters 1-4 from any given year from GetDate().
Not sure if this is something that's built in or I have to write a function for.
Thanks!

This is simple, but does the trick. You would set #date to any given value. I used getdate().
declare #date datetime = getdate()
declare #year int = datepart(year, #date)
select #year as [year]
,datepart(iso_week, cast('1/1/' + cast(#year as char(4)) as date)) as ISOWeekQ1
,datepart(iso_week, cast('4/1/' + cast(#year as char(4)) as date)) as ISOWeekQ2
,datepart(iso_week, cast('7/1/' + cast(#year as char(4)) as date)) as ISOWeekQ3
,datepart(iso_week, cast('10/1/' + cast(#year as char(4)) as date)) as ISOWeekQ4
For me, this returned:
year ISOWeekQ1 ISOWeekQ2 ISOWeekQ3 ISOWeekQ4
----------- ----------- ----------- ----------- -----------
2017 52 13 26 39
This also works, and doesn't use cast() or risk date conversion errors for different formats of the date (e.g., yyyy/mm/dd):
declare #date datetime = getdate()
set #date = dateadd(day, - datepart(dayofyear, #date) + 1, #date) -- sets date to Jan 1
select datepart(year, #date) [year]
,datepart(iso_week, #date) as ISOWeekQ1
,datepart(iso_week, dateadd(month, 3, #date)) as ISOWeekQ2
,datepart(iso_week, dateadd(month, 6, #date)) as ISOWeekQ3
,datepart(iso_week, dateadd(month, 9, #date)) as ISOWeekQ4
The output of this query is the same as the first.

Datetime2 Overflow Issue [duplicate]

I have a table listing people along with their date of birth (currently a nvarchar(25))
How can I convert that to a date, and then calculate their age in years?
My data looks as follows
ID Name DOB
1 John 1992-01-09 00:00:00
2 Sally 1959-05-20 00:00:00
I would like to see:
ID Name AGE DOB
1 John 17 1992-01-09 00:00:00
2 Sally 50 1959-05-20 00:00:00

There are issues with leap year/days and the following method, see the update below:
try this:
DECLARE #dob datetime
SET #dob='1992-01-09 00:00:00'
SELECT DATEDIFF(hour,#dob,GETDATE())/8766.0 AS AgeYearsDecimal
,CONVERT(int,ROUND(DATEDIFF(hour,#dob,GETDATE())/8766.0,0)) AS AgeYearsIntRound
,DATEDIFF(hour,#dob,GETDATE())/8766 AS AgeYearsIntTrunc
OUTPUT:
AgeYearsDecimal AgeYearsIntRound AgeYearsIntTrunc
--------------------------------------- ---------------- ----------------
17.767054 18 17
(1 row(s) affected)
UPDATE here are some more accurate methods:
BEST METHOD FOR YEARS IN INT
DECLARE #Now datetime, #Dob datetime
SELECT #Now='1990-05-05', #Dob='1980-05-05' --results in 10
--SELECT #Now='1990-05-04', #Dob='1980-05-05' --results in 9
--SELECT #Now='1989-05-06', #Dob='1980-05-05' --results in 9
--SELECT #Now='1990-05-06', #Dob='1980-05-05' --results in 10
--SELECT #Now='1990-12-06', #Dob='1980-05-05' --results in 10
--SELECT #Now='1991-05-04', #Dob='1980-05-05' --results in 10
SELECT
(CONVERT(int,CONVERT(char(8),#Now,112))-CONVERT(char(8),#Dob,112))/10000 AS AgeIntYears
you can change the above 10000 to 10000.0 and get decimals, but it will not be as accurate as the method below.
BEST METHOD FOR YEARS IN DECIMAL
DECLARE #Now datetime, #Dob datetime
SELECT #Now='1990-05-05', #Dob='1980-05-05' --results in 10.000000000000
--SELECT #Now='1990-05-04', #Dob='1980-05-05' --results in 9.997260273973
--SELECT #Now='1989-05-06', #Dob='1980-05-05' --results in 9.002739726027
--SELECT #Now='1990-05-06', #Dob='1980-05-05' --results in 10.002739726027
--SELECT #Now='1990-12-06', #Dob='1980-05-05' --results in 10.589041095890
--SELECT #Now='1991-05-04', #Dob='1980-05-05' --results in 10.997260273973
SELECT 1.0* DateDiff(yy,#Dob,#Now)
+CASE
WHEN #Now >= DATEFROMPARTS(DATEPART(yyyy,#Now),DATEPART(m,#Dob),DATEPART(d,#Dob)) THEN --birthday has happened for the #now year, so add some portion onto the year difference
( 1.0 --force automatic conversions from int to decimal
* DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),DATEPART(m,#Dob),DATEPART(d,#Dob)),#Now) --number of days difference between the #Now year birthday and the #Now day
/ DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),1,1),DATEFROMPARTS(DATEPART(yyyy,#Now)+1,1,1)) --number of days in the #Now year
)
ELSE --birthday has not been reached for the last year, so remove some portion of the year difference
-1 --remove this fractional difference onto the age
* ( -1.0 --force automatic conversions from int to decimal
* DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),DATEPART(m,#Dob),DATEPART(d,#Dob)),#Now) --number of days difference between the #Now year birthday and the #Now day
/ DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),1,1),DATEFROMPARTS(DATEPART(yyyy,#Now)+1,1,1)) --number of days in the #Now year
)
END AS AgeYearsDecimal

Gotta throw this one out there. If you convert the date using the 112 style (yyyymmdd) to a number you can use a calculation like this...
(yyyyMMdd - yyyyMMdd) / 10000 = difference in full years
declare #as_of datetime, #bday datetime;
select #as_of = '2009/10/15', #bday = '1980/4/20'
select
Convert(Char(8),#as_of,112),
Convert(Char(8),#bday,112),
0 + Convert(Char(8),#as_of,112) - Convert(Char(8),#bday,112),
(0 + Convert(Char(8),#as_of,112) - Convert(Char(8),#bday,112)) / 10000
output
20091015 19800420 290595 29

I have used this query in our production code for nearly 10 years:
SELECT FLOOR((CAST (GetDate() AS INTEGER) - CAST(Date_of_birth AS INTEGER)) / 365.25) AS Age

You need to consider the way the datediff command rounds.
SELECT CASE WHEN dateadd(year, datediff (year, DOB, getdate()), DOB) > getdate()
THEN datediff(year, DOB, getdate()) - 1
ELSE datediff(year, DOB, getdate())
END as Age
FROM <table>
Which I adapted from here.
Note that it will consider 28th February as the birthday of a leapling for non-leap years e.g. a person born on 29 Feb 2020 will be considered 1 year old on 28 Feb 2021 instead of 01 Mar 2021.

So many of the above solutions are wrong DateDiff(yy,#Dob, #PassedDate) will not consider the month and day of both dates. Also taking the dart parts and comparing only works if they're properly ordered.
THE FOLLOWING CODE WORKS AND IS VERY SIMPLE:
create function [dbo].[AgeAtDate](
#DOB datetime,
#PassedDate datetime
)
returns int
with SCHEMABINDING
as
begin
declare #iMonthDayDob int
declare #iMonthDayPassedDate int
select #iMonthDayDob = CAST(datepart (mm,#DOB) * 100 + datepart (dd,#DOB) AS int)
select #iMonthDayPassedDate = CAST(datepart (mm,#PassedDate) * 100 + datepart (dd,#PassedDate) AS int)
return DateDiff(yy,#DOB, #PassedDate)
- CASE WHEN #iMonthDayDob <= #iMonthDayPassedDate
THEN 0
ELSE 1
END
End

EDIT: THIS ANSWER IS INCORRECT. I leave it in here as a warning to anyone tempted to use dayofyear, with a further edit at the end.
If, like me, you do not want to divide by fractional days or risk rounding/leap year errors, I applaud #Bacon Bits comment in a post above https://stackoverflow.com/a/1572257/489865 where he says:
If we're talking about human ages, you should calculate it the way
humans calculate age. It has nothing to do with how fast the earth
moves and everything to do with the calendar. Every time the same
month and day elapses as the date of birth, you increment age by 1.
This means the following is the most accurate because it mirrors what
humans mean when they say "age".
He then offers:
DATEDIFF(yy, #date, GETDATE()) -
CASE WHEN (MONTH(#date) > MONTH(GETDATE())) OR (MONTH(#date) = MONTH(GETDATE()) AND DAY(#date) > DAY(GETDATE()))
THEN 1 ELSE 0 END
There are several suggestions here involving comparing the month & day (and some get it wrong, failing to allow for the OR as correctly here!). But nobody has offered dayofyear, which seems so simple and much shorter. I offer:
DATEDIFF(year, #date, GETDATE()) -
CASE WHEN DATEPART(dayofyear, #date) > DATEPART(dayofyear, GETDATE()) THEN 1 ELSE 0 END
[Note: Nowhere in SQL BOL/MSDN is what DATEPART(dayofyear, ...) returns actually documented! I understand it to be a number in the range 1--366; most importantly, it does not change by locale as per DATEPART(weekday, ...) & SET DATEFIRST.]
EDIT: Why dayofyear goes wrong: As user #AeroX has commented, if the birth/start date is after February in a non leap year, the age is incremented one day early when the current/end date is a leap year, e.g. '2015-05-26', '2016-05-25' gives an age of 1 when it should still be 0. Comparing the dayofyear in different years is clearly dangerous. So using MONTH() and DAY() is necessary after all.

I believe this is similar to other ones posted here.... but this solution worked for the leap year examples 02/29/1976 to 03/01/2011 and also worked for the case for the first year.. like 07/04/2011 to 07/03/2012 which the last one posted about leap year solution did not work for that first year use case.
SELECT FLOOR(DATEDIFF(DAY, #date1 , #date2) / 365.25)
Found here.

Since there isn't one simple answer that always gives the correct age, here's what I came up with.
SELECT DATEDIFF(YY, DateOfBirth, GETDATE()) -
CASE WHEN RIGHT(CONVERT(VARCHAR(6), GETDATE(), 12), 4) >=
RIGHT(CONVERT(VARCHAR(6), DateOfBirth, 12), 4)
THEN 0 ELSE 1 END AS AGE
This gets the year difference between the birth date and the current date. Then it subtracts a year if the birthdate hasn't passed yet.
Accurate all the time - regardless of leap years or how close to the birthdate.
Best of all - no function.

I've done a lot of thinking and searching about this and I have 3 solutions that
calculate age correctly
are short (mostly)
are (mostly) very understandable.
Here are testing values:
DECLARE #NOW DATETIME = '2013-07-04 23:59:59'
DECLARE #DOB DATETIME = '1986-07-05'
Solution 1: I found this approach in one js library. It's my favourite.
DATEDIFF(YY, #DOB, #NOW) -
CASE WHEN DATEADD(YY, DATEDIFF(YY, #DOB, #NOW), #DOB) > #NOW THEN 1 ELSE 0 END
It's actually adding difference in years to DOB and if it is bigger than current date then subtracts one year. Simple right? The only thing is that difference in years is duplicated here.
But if you don't need to use it inline you can write it like this:
DECLARE #AGE INT = DATEDIFF(YY, #DOB, #NOW)
IF DATEADD(YY, #AGE, #DOB) > #NOW
SET #AGE = #AGE - 1
Solution 2: This one I originally copied from #bacon-bits. It's the easiest to understand but a bit long.
DATEDIFF(YY, #DOB, #NOW) -
CASE WHEN MONTH(#DOB) > MONTH(#NOW)
OR MONTH(#DOB) = MONTH(#NOW) AND DAY(#DOB) > DAY(#NOW)
THEN 1 ELSE 0 END
It's basically calculating age as we humans do.
Solution 3: My friend refactored it into this:
DATEDIFF(YY, #DOB, #NOW) -
CEILING(0.5 * SIGN((MONTH(#DOB) - MONTH(#NOW)) * 50 + DAY(#DOB) - DAY(#NOW)))
This one is the shortest but it's most difficult to understand. 50 is just a weight so the day difference is only important when months are the same. SIGN function is for transforming whatever value it gets to -1, 0 or 1. CEILING(0.5 * is the same as Math.max(0, value) but there is no such thing in SQL.

What about:
DECLARE #DOB datetime
SET #DOB='19851125'
SELECT Datepart(yy,convert(date,GETDATE())-#DOB)-1900
Wouldn't that avoid all those rounding, truncating and ofsetting issues?

Just check whether the below answer is feasible.
DECLARE #BirthDate DATE = '09/06/1979'
SELECT
(
YEAR(GETDATE()) - YEAR(#BirthDate) -
CASE WHEN (MONTH(GETDATE()) * 100) + DATEPART(dd, GETDATE()) >
(MONTH(#BirthDate) * 100) + DATEPART(dd, #BirthDate)
THEN 1
ELSE 0
END
)

select floor((datediff(day,0,#today) - datediff(day,0,#birthdate)) / 365.2425) as age
There are a lot of 365.25 answers here. Remember how leap years are defined:
Every four years
except every 100 years
except every 400 years

There are many answers to this question, but I think this one is close to the truth.
The datediff(year,…,…) function, as we all know, only counts the boundaries crossed by the date part, in this case the year. As a result it ignores the rest of the year.
This will only give the age in completed years if the year were to start on the birthday. It probably doesn’t, but we can fake it by adjusting the asking date back by the same amount.
In pseudopseudo code, it’s something like this:
adjusted_today = today - month(dob) + 1 - day(dob) + 1
age = year(adjusted_today - dob)
The + 1 is to allow for the fact that the month and day numbers start from 1 and not 0.
The reason we subtract the month and the day separately rather than the day of the year is because February has the annoying tendency to change its length.
The calculation in SQL is:
datediff(year,dob,dateadd(month,-month(dob)+1,dateadd(day,-day(dob)+1,today)))
where dob and today are presumed to be the date of birth and the asking date.
You can test this as follows:
WITH dates AS (
SELECT
cast('2022-03-01' as date) AS today,
cast('1943-02-25' as date) AS dob
)
select
datediff(year,dob,dateadd(month,-month(dob)+1,dateadd(day,-day(dob)+1,today))) AS age
from dates;
which gives you George Harrison’s age in completed years.
This is much cleaner than fiddling about with quarter days which will generally give you misleading values on the edges.
If you have the luxury of creating a scalar function, you can use something like this:
DROP FUNCTION IF EXISTS age;
GO
CREATE FUNCTION age(#dob date, #today date) RETURNS INT AS
BEGIN
SET #today = dateadd(month,-month(#dob)+1,#today);
SET #today = dateadd(day,-day(#dob)+1,#today);
RETURN datediff(year,#dob,#today);
END;
GO
Remember, you need to call dbo.age() because, well, Microsoft.

DECLARE #DOB datetime
set #DOB ='11/25/1985'
select floor(
( cast(convert(varchar(8),getdate(),112) as int)-
cast(convert(varchar(8),#DOB,112) as int) ) / 10000
)
source: http://beginsql.wordpress.com/2012/04/26/how-to-calculate-age-in-sql-server/

Try This
DECLARE #date datetime, #tmpdate datetime, #years int, #months int, #days int
SELECT #date = '08/16/84'
SELECT #tmpdate = #date
SELECT #years = DATEDIFF(yy, #tmpdate, GETDATE()) - CASE WHEN (MONTH(#date) > MONTH(GETDATE())) OR (MONTH(#date) = MONTH(GETDATE()) AND DAY(#date) > DAY(GETDATE())) THEN 1 ELSE 0 END
SELECT #tmpdate = DATEADD(yy, #years, #tmpdate)
SELECT #months = DATEDIFF(m, #tmpdate, GETDATE()) - CASE WHEN DAY(#date) > DAY(GETDATE()) THEN 1 ELSE 0 END
SELECT #tmpdate = DATEADD(m, #months, #tmpdate)
SELECT #days = DATEDIFF(d, #tmpdate, GETDATE())
SELECT Convert(Varchar(Max),#years)+' Years '+ Convert(Varchar(max),#months) + ' Months '+Convert(Varchar(Max), #days)+'days'

After trying MANY methods, this works 100% of the time using the modern MS SQL FORMAT function instead of convert to style 112. Either would work but this is the least code.
Can anyone find a date combination which does not work? I don't think there is one :)
--Set parameters, or choose from table.column instead:
DECLARE #DOB DATE = '2000/02/29' -- If #DOB is a leap day...
,#ToDate DATE = '2018/03/01' --...there birthday in this calculation will be
--0+ part tells SQL to calc the char(8) as numbers:
SELECT [Age] = (0+ FORMAT(#ToDate,'yyyyMMdd') - FORMAT(#DOB,'yyyyMMdd') ) /10000

CASE WHEN datepart(MM, getdate()) < datepart(MM, BIRTHDATE) THEN ((datepart(YYYY, getdate()) - datepart(YYYY, BIRTH_DATE)) -1 )
ELSE
CASE WHEN datepart(MM, getdate()) = datepart(MM, BIRTHDATE)
THEN
CASE WHEN datepart(DD, getdate()) < datepart(DD, BIRTHDATE) THEN ((datepart(YYYY, getdate()) - datepart(YYYY, BIRTHDATE)) -1 )
ELSE (datepart(YYYY, getdate()) - datepart(YYYY, BIRTHDATE))
END
ELSE (datepart(YYYY, getdate()) - datepart(YYYY, BIRTHDATE)) END
END

SELECT ID,
Name,
DATEDIFF(yy,CONVERT(DATETIME, DOB),GETDATE()) AS AGE,
DOB
FROM MyTable

How about this:
SET #Age = CAST(DATEDIFF(Year, #DOB, #Stamp) as int)
IF (CAST(DATEDIFF(DAY, DATEADD(Year, #Age, #DOB), #Stamp) as int) < 0)
SET #Age = #Age - 1

Try this solution:
declare #BirthDate datetime
declare #ToDate datetime
set #BirthDate = '1/3/1990'
set #ToDate = '1/2/2008'
select #BirthDate [Date of Birth], #ToDate [ToDate],(case when (DatePart(mm,#ToDate) < Datepart(mm,#BirthDate))
OR (DatePart(m,#ToDate) = Datepart(m,#BirthDate) AND DatePart(dd,#ToDate) < Datepart(dd,#BirthDate))
then (Datepart(yy, #ToDate) - Datepart(yy, #BirthDate) - 1)
else (Datepart(yy, #ToDate) - Datepart(yy, #BirthDate))end) Age

This will correctly handle the issues with the birthday and rounding:
DECLARE #dob datetime
SET #dob='1992-01-09 00:00:00'
SELECT DATEDIFF(YEAR, '0:0', getdate()-#dob)

Ed Harper's solution is the simplest I have found which never returns the wrong answer when the month and day of the two dates are 1 or less days apart. I made a slight modification to handle negative ages.
DECLARE #D1 AS DATETIME, #D2 AS DATETIME
SET #D2 = '2012-03-01 10:00:02'
SET #D1 = '2013-03-01 10:00:01'
SELECT
DATEDIFF(YEAR, #D1,#D2)
+
CASE
WHEN #D1<#D2 AND DATEADD(YEAR, DATEDIFF(YEAR,#D1, #D2), #D1) > #D2
THEN - 1
WHEN #D1>#D2 AND DATEADD(YEAR, DATEDIFF(YEAR,#D1, #D2), #D1) < #D2
THEN 1
ELSE 0
END AS AGE

The answer marked as correct is nearer to accuracy but, it fails in following scenario - where Year of birth is Leap year and day are after February month
declare #ReportStartDate datetime = CONVERT(datetime, '1/1/2014'),
#DateofBirth datetime = CONVERT(datetime, '2/29/1948')
FLOOR(DATEDIFF(HOUR,#DateofBirth,#ReportStartDate )/8766)
OR
FLOOR(DATEDIFF(HOUR,#DateofBirth,#ReportStartDate )/8765.82) -- Divisor is more accurate than 8766
-- Following solution is giving me more accurate results.
FLOOR(DATEDIFF(YEAR,#DateofBirth,#ReportStartDate) - (CASE WHEN DATEADD(YY,DATEDIFF(YEAR,#DateofBirth,#ReportStartDate),#DateofBirth) > #ReportStartDate THEN 1 ELSE 0 END ))
It worked in almost all scenarios, considering leap year, date as 29 feb, etc.
Please correct me if this formula have any loophole.

Declare #dob datetime
Declare #today datetime
Set #dob = '05/20/2000'
set #today = getdate()
select CASE
WHEN dateadd(year, datediff (year, #dob, #today), #dob) > #today
THEN datediff (year, #dob, #today) - 1
ELSE datediff (year, #dob, #today)
END as Age

Here is how i calculate age given a birth date and current date.
select case
when cast(getdate() as date) = cast(dateadd(year, (datediff(year, '1996-09-09', getdate())), '1996-09-09') as date)
then dateDiff(yyyy,'1996-09-09',dateadd(year, 0, getdate()))
else dateDiff(yyyy,'1996-09-09',dateadd(year, -1, getdate()))
end as MemberAge
go

CREATE function dbo.AgeAtDate(
#DOB datetime,
#CompareDate datetime
)
returns INT
as
begin
return CASE WHEN #DOB is null
THEN
null
ELSE
DateDiff(yy,#DOB, #CompareDate)
- CASE WHEN datepart(mm,#CompareDate) > datepart(mm,#DOB) OR (datepart(mm,#CompareDate) = datepart(mm,#DOB) AND datepart(dd,#CompareDate) >= datepart(dd,#DOB))
THEN 0
ELSE 1
END
END
End
GO

DECLARE #FromDate DATETIME = '1992-01-2623:59:59.000',
#ToDate DATETIME = '2016-08-10 00:00:00.000',
#Years INT, #Months INT, #Days INT, #tmpFromDate DATETIME
SET #Years = DATEDIFF(YEAR, #FromDate, #ToDate)
- (CASE WHEN DATEADD(YEAR, DATEDIFF(YEAR, #FromDate, #ToDate),
#FromDate) > #ToDate THEN 1 ELSE 0 END)
SET #tmpFromDate = DATEADD(YEAR, #Years , #FromDate)
SET #Months = DATEDIFF(MONTH, #tmpFromDate, #ToDate)
- (CASE WHEN DATEADD(MONTH,DATEDIFF(MONTH, #tmpFromDate, #ToDate),
#tmpFromDate) > #ToDate THEN 1 ELSE 0 END)
SET #tmpFromDate = DATEADD(MONTH, #Months , #tmpFromDate)
SET #Days = DATEDIFF(DAY, #tmpFromDate, #ToDate)
- (CASE WHEN DATEADD(DAY, DATEDIFF(DAY, #tmpFromDate, #ToDate),
#tmpFromDate) > #ToDate THEN 1 ELSE 0 END)
SELECT #FromDate FromDate, #ToDate ToDate,
#Years Years, #Months Months, #Days Days

What about a solution with only date functions, not math, not worries about leap year
CREATE FUNCTION dbo.getAge(#dt datetime)
RETURNS int
AS
BEGIN
RETURN
DATEDIFF(yy, #dt, getdate())
- CASE
WHEN
MONTH(#dt) > MONTH(GETDATE()) OR
(MONTH(#dt) = MONTH(GETDATE()) AND DAY(#dt) > DAY(GETDATE()))
THEN 1
ELSE 0
END
END

declare #birthday as datetime
set #birthday = '2000-01-01'
declare #today as datetime
set #today = GetDate()
select
case when ( substring(convert(varchar, #today, 112), 5,4) >= substring(convert(varchar, #birthday, 112), 5,4) ) then
(datepart(year,#today) - datepart(year,#birthday))
else
(datepart(year,#today) - datepart(year,#birthday)) - 1
end

The following script checks the difference in years between now and the given date of birth; the second part checks whether the birthday is already past in the current year; if not, it subtracts it:
SELECT year(NOW()) - year(date_of_birth) - (CONCAT(year(NOW()), '-', month(date_of_birth), '-', day(date_of_birth)) > NOW()) AS Age
FROM tableName;

How to grab data from the last 13 months?

So I have this code, this is for grabbing data for the last 11 month of sale including the current month, make it a whole year. What do I have to do to change it to grabbing data for the last 12 months plus current month? I know I have to change something on the right(select period)... but not sure
In this one, the left function shows how to get the current year (2014 ) minus 1 to give 2013.. but I don't understand the right function, what does 2 mean?
Thanks
period <= (
SELECT Period
FROM dbo.FiscalDates
WHERE (Date = CONVERT(varchar(10), GETDATE(), 102))) and period >= (
convert(varchar, left((
SELECT Period
FROM dbo.FiscalDates
WHERE (Date = CONVERT(varchar(10), GETDATE(), 102))),4)-1)+'-'+
convert(varchar, right((
SELECT Period
FROM dbo.FiscalDates
WHERE (Date = CONVERT(varchar(10), GETDATE(), 102))),2)))
group by prodnum, period, WhseNum

Whoah buddy I think you may be overcomplicating things here. If you want to get data for the past X number of months then just use DATEADD it's a very useful function.
All you need to do then is
select
YourColumns
FROM YourTable
WHERE YourDate >= DATEADD(MONTH, -13, CAST(GETDATE() AS DATE))
and bam there you go.

DECLARE
#FormYear AS INT,
#FormMonth AS INT,
#ToYear AS INT,
#ToMonth AS INT,
#FromDate AS DATE,
#ToDate AS DATE
SET #FormYear=YEAR(DATEADD(DAY, -365, GETDATE()))
SET #FormMonth=MONTH(DATEADD(DAY, -365, GETDATE()))
SET #ToYear=YEAR(GETDATE())
SET #ToMonth=MONTH(GETDATE())
SET #FromDate= CAST(CAST(#FormMonth AS VARCHAR) +'-'+'01'+ '-' +CAST(#FormYear AS VARCHAR) AS DATE)
SET #ToDate= CAST(CAST(#ToMonth AS VARCHAR) +'-' + '01'+'-' + CAST(#ToYear AS VARCHAR) AS DATE)
After that, just select-
YourDateField Between #FormDate AND #ToDate

convert datetime to display full month

I have searched and i cannot seem to find the answer. I have tried using different styles, but none of them give me exactly what i want.
I am trying to convert a datetime, that I have calculated. However I need it to display the full month.
SELECT CONVERT(VARCHAR(25),DATEADD(dd, #codelife, getdate()),107)
the above line works fine, EXCEPT it displays the date like
Feb 27, 2014
I need it to display date like
February 27, 2014 etc.....
any suggestions?

Nathan's answer seems solid, however if you're using SQL Server 2012 you can make use of the FORMAT() function:
SELECT FORMAT(GETDATE(),'MMMM dd, yyyy')
Or in your case:
SELECT FORMAT(DATEADD(dd, #codelife, getdate()),'MMMM dd, yyyy')

I always use http://www.sql-server-helper.com/tips/date-formats.aspx as my reference
SELECT DATENAME(MM, GETDATE()) + RIGHT(CONVERT(VARCHAR(12), GETDATE(), 107), 9) AS [Month DD, YYYY]
I would declare your date as a variable and do something like:
DECLARE #myDate DATETIME
SET #myDate = DateAdd(dd, #codelife, getdate());
SELECT DATENAME(MM, #myDate) + RIGHT(CONVERT(VARCHAR(12), #myDate, 107), 9) AS [Month DD, YYYY]

You may have to do it in 2 steps.
DECLARE #codelife INT = 120
DECLARE #codedate DATETIME = (SELECT (DATEADD(D, #codelife, GETDATE())))
SELECT DATENAME(MM, #codedate) + SUBSTRING(CONVERT(VARCHAR(25), #codedate, 107), 4, 25)

SELECT DATENAME(MONTH, GETDATE())
+ RIGHT(CONVERT(VARCHAR(12), GETDATE(), 107), 9) AS [Month DD, YYYY]
OR Date without Comma Between date and year, you can use the following
SELECT DATENAME(MONTH, GETDATE()) + ' ' + CAST(DAY(GETDATE()) AS VARCHAR(2))
+ ' ' + CAST(YEAR(GETDATE()) AS VARCHAR(4)) AS [Month DD YYYY]
I answered the same question a couple of days ago have a look here sql server Get the FULL month name from a date

Get last Friday's Date unless today is Friday using T-SQL

I'm trying to get the correct SQL code to obtain last Friday's date. A few days ago, I thought I had my code correct. But just noticed that it's getting last week's Friday date, not the last Friday. The day I'm writing this question is Saturday, 8/11/2012 # 12:23am. In SQL Server, this code is returning Friday, 8/3/2012. However, I want this to return Friday, 8/10/2012 instead. How can I fix this code? Since we're getting to specifics here, if the current day is Friday, then I want to return today's date. So if it were yesterday (8/10/2012) and I ran this code yesterday, then I would want this code to return 8/10/2012, not 8/3/2012.
SELECT DATEADD(DAY, -3, DATEADD(WEEK, DATEDIFF(WEEK, 0, GETDATE()), 0))

try this:
declare #date datetime;
set #date='2012-08-09'
SELECT case when datepart(weekday, #date) >5 then
DATEADD(DAY, +4, DATEADD(WEEK, DATEDIFF(WEEK, 0, #date), 0))
else DATEADD(DAY, -3, DATEADD(WEEK, DATEDIFF(WEEK, 0, #date), 0)) end
result:
2012-08-03
Example2:
declare #date datetime;
set #date='2012-08-10'
SELECT case when datepart(weekday, #date) >5 then
DATEADD(DAY, +4, DATEADD(WEEK, DATEDIFF(WEEK, 0, #date), 0))
else DATEADD(DAY, -3, DATEADD(WEEK, DATEDIFF(WEEK, 0, #date), 0)) end
result:
2012-08-10

Modular arithmetic is the most direct approach, and order of operations decides how Fridays are treated:
DECLARE #test_date DATETIME = '2012-09-28'
SELECT DATEADD(d,-1-(DATEPART(dw,#test_date) % 7),#test_date) AS Last_Friday
,DATEADD(d,-(DATEPART(dw,#test_date+1) % 7),#test_date) AS This_Friday

Use this :
SELECT DATEADD(day, (DATEDIFF (day, '19800104', CURRENT_TIMESTAMP) / 7) * 7, '19800104') as Last_Friday

None of that? Try this:
DECLARE #D DATE = GETDATE()
SELECT DATEADD(D,-(DATEPART(W,#D)+1)%7,#D)

A tested function which works no matter what ##DATEFIRST is set to.
-- ==============
-- fn_Get_Week_Ending_forDate
-- Author: Shawn C. Teague
-- Create date: 2017
-- Modified date:
-- Description: Returns the Week Ending Date on DayOfWeek for a given stop date
-- Parameters: DayOfWeek varchar(10) i.e. Monday,Tues,Wed,Friday,Sat,Su,1-7
-- DateInWeek DATE
-- ==============
CREATE FUNCTION [dbo].[fn_Get_Week_Ending_forDate] (
#DayOfWeek VARCHAR(10),#DateInWeek DATE)
RETURNS DATE
AS
BEGIN
DECLARE #End_Date DATE
,#DoW TINYINT
SET #DoW = CASE WHEN ISNUMERIC(#DayOfWeek) = 1
THEN CAST(#DayOfWeek AS TINYINT)
WHEN #DayOfWeek like 'Su%' THEN 1
WHEN #DayOfWeek like 'M%' THEN 2
WHEN #DayOfWeek like 'Tu%' THEN 3
WHEN #DayOfWeek like 'W%' THEN 4
WHEN #DayOfWeek like 'Th%' THEN 5
WHEN #DayOfWeek like 'F%' THEN 6
ELSE 7
END
select #End_Date =
CAST(DATEADD(DAY,
CASE WHEN (#DoW - (((##datefirst) + datepart(weekday, #DateInWeek)) % 7)) = 7
THEN 0
WHEN (#DoW - (((##datefirst) + datepart(weekday, #DateInWeek)) % 7)) < 0
THEN 7 - ABS(#DoW - (((##datefirst) + datepart(weekday, #DateInWeek)) % 7))
ELSE (#DoW - (((##datefirst) + datepart(weekday, #DateInWeek)) % 7) )
END
,#DateInWeek) AS DATE)
RETURN #End_Date
END

This will give you the Friday of Last week.
SELECT DATEADD(day, -3 - (DATEPART(dw, GETDATE()) + ##DATEFIRST - 2) % 7, GETDATE()) AS LastWeekFriday
This will give you last Friday's Date.
SELECT DATEADD(day, +4 - (DATEPART(dw, GETDATE()) + ##DATEFIRST-2) % 7, GETDATE()) AS LastFriday

select convert(varchar(10),dateadd(d, -((datepart(weekday, getdate()) + 1 + ##DATEFIRST) % 7), getdate()),101)

Following code can be use to return any last day by replacing #dw_wk, test case below use friday as asked in original questions
DECLARE #date SMALLDATETIME
,#dw_wk INT --last day of week required - its integer representation
,#dw_day int --current day integer reprsentation
SELECT #date='8/11/2012'
SELECT #dw_day=DATEPART(dw,#date)
SELECT #dw_wk=DATEPART(dw,'1/2/2015') --Just trying not to hard code 5 for friday, here we can substitute with any date which is friday
SELECT case when #dw_day<#dw_wk then DATEADD(DAY, #dw_wk-7-#dw_day,#date) else DATEADD(DAY,#dw_wk-#dw_day, #date) END

Here's an answer I found here adapted from MySQL to T-SQL that is a one liner using all basic arithmetic (no division or modulos):
SELECT DATEADD(d, 1 - datepart(weekday, dateadd(d, 2, GETDATE())), GETDATE())
You can do all sorts of combinations of this, like get next Friday's date unless today is Friday, or get last Thursday's date unless today is Thursday by just changing the 1 and the 2 literals in the command:
Get next Friday's date unless today is Friday
SELECT DATEADD(d, 7 - datepart(weekday, dateadd(d, 1, GETDATE())), GETDATE())
Get last Thursday's date unless today is Thursday
SELECT DATEADD(d, 1 - datepart(weekday, dateadd(d, 3, GETDATE())), GETDATE())

I have had this same issue, and created the following example to show how to do this and to make it flexible to use whichever day of the week you want. I have different lines in the SELECT statement, just to show what this is doing, but you just need the [Results] line to get the answer. I also used variables for the current date and the target day of the week, to make it easier to see what needs to change.
Finally, there is an example of results when you want to include the current date as a possible example or when you always want to go back to the previous week.
DECLARE #GetDate AS DATETIME = GETDATE();
DECLARE #Target INT = 6 -- 6 = Friday
SELECT
#GetDate AS [Current Date] ,
DATEPART(dw, #GetDate) AS [Current Day of Week],
#Target AS [Target Day of Week] ,
IIF(#Target = DATEPART(dw, #GetDate), 'Yes' , 'No') AS [IsMatch] ,
IIF(#Target = DATEPART(dw, #GetDate), 0 , ((7 + #Target - DATEPART(dw, #GetDate)) % 7) - 7) AS [DateAdjust] ,
------------------------------------------------------------------------------------------------------------------------------------------------
CAST(IIF(#Target = DATEPART(dw, #GetDate), #GetDate, DATEADD(d, (((7 + #Target - DATEPART(dw, #GetDate)) % 7) - 7), #GetDate)) AS DATE) AS [Result]
------------------------------------------------------------------------------------------------------------------------------------------------
;
SELECT
#GetDate AS [Current Date] ,
DATEPART(dw, #GetDate) AS [Current Day of Week],
#Target AS [Target Day of Week] ,
((7 + #Target - DATEPART(dw, #GetDate)) % 7) - 7 AS [DateAdjust] ,
------------------------------------------------------------------------------------------------------------------------------------------------
CAST(DATEADD(d, (((7 + #Target - DATEPART(dw, #GetDate)) % 7) - 7), #GetDate) AS DATE) AS [NOTIncludeCurrent]
------------------------------------------------------------------------------------------------------------------------------------------------
;

SELECT DECODE(TO_CHAR(SYSDATE,'DY'),'FRI',SYSDATE,NEXT_DAY(SYSDATE, 'FRI')-7) FROM dual;