Find Number Of days and Months and years between 2 Dates - tsql

I am trying to Get Years, months and no. of days between 2 dates.
But when dates are like below, it gives wrong output (Month part of FromDate is greater than Todate).
declare #FromDate date='2010-10-27'
declare #Todate date='2012-03-02'
SELECT
DATEDIFF( mm, #FromDate, #ToDate) / 12 AS years
, datediff(mm,#FromDate, #ToDate) % 12 AS months
, DATEDIFF( dd, DATEADD( mm, DATEDIFF( mm, #FromDate, #ToDate), #FromDate), #ToDate) as Days
**It Shows Output as**
Years Months days
1 5 -25
It should be 4 months and 29 days. Please tell me how can I get desired Output.
Thanks in Advance


The following might solve the problem - but I think, the correct values would be 1 year, 4 month and 4 days!?
declare #start date = '2010-10-27'
declare #ende date = '2012-03-02'
SELECT DATEDIFF(mm, #start, #ende)/12 MyYears
,(DATEDIFF(mm, #start, #ende)%12)-1 MyMonths
,DATEDIFF(dd, DATEADD(mm, (DATEDIFF(mm, #start, #ende)%12)-1,DATEADD(yy, DATEDIFF(mm, #start, #ende)/12, #Start)), #Ende) MyDays
--Check of result
SELECT dateadd(dd, 4, dateadd(mm, 4, dateadd(yy, 1, #start))) x


I used this. This gives the desired result.
(#FromDate date,
#ToDate Date
)
DECLARE #Years INT, #Months INT, #Days INT
SET #Years = DATEDIFF(YEAR, #FromDate, #ToDate)
IF DATEADD(YY, #Years, #FromDate) > #ToDate
BEGIN
SET #Years = #Years - 1
END
SET #FromDate = DATEADD(YY, #Years, #FromDate)
SET #Months = DATEDIFF(MM, #FromDate, #ToDate)
IF DATEADD(MM, #Months, #FromDate) > #ToDate
BEGIN
SET #Months = #Months - 1
END
SET #FromDate = DATEADD(MM, #Months, #FromDate)
SET #Days = DATEDIFF(DD, #FromDate, #ToDate)
Select #Years as Years,#Months as Months,
#Days as Days


Maybe this is Correct
declare #FromDate date='2010-10-27'
declare #Todate date='2012-03-02'
SELECT
DATEDIFF( yy,#FromDate,#Todate) AS YEARS,
DATEDIFF( mm,#FromDate,#Todate) AS MONTHS,
DATEDIFF( dd,#FromDate,#Todate) AS DAYS

Related

How can I get T-SQL to include correct data from last month

In the below query I return data for past 5 months, unfortunately I can not get it to include correct count from current month (June 2021), it ruturns 0 where as it should have returned 2 since I have 2 entries with StartDate 14-06-2021 and 17-06-2021 which should have been in this count.. How can I fix this?.
The output I get (missing 2 in month 6)
year month EmployeeStartet
2021 2 8
2021 3 0
2021 4 0
2021 5 4
2021 6 0
My Query
declare #thismonth1 as Date = DateAdd(
d,
1 - DatePart(d, CURRENT_TIMESTAMP),
CURRENT_TIMESTAMP
);
declare #lastMonth1 as Date = DateAdd(
d,
1 - DatePart(d, CURRENT_TIMESTAMP),
CURRENT_TIMESTAMP
);
declare #firstMonth1 as Date = DateAdd(m, -4, #lastMonth1);
WITH months AS (
SELECT
#firstMonth1 AS thisMonth
UNION ALL
SELECT
DateAdd(m, 1, thisMonth) AS thisMonth
FROM
months
WHERE
thisMonth < #lastMonth1
),
data AS (
SELECT
YEAR(StartDate) year,
MONTH(StartDate) month,
COUNT(StartDate) EmployeeStartet
FROM
EFP_EmploymentUser
WHERE
EmployType = 'fixed'
AND StartDate BETWEEN #firstmonth1
AND #thismonth1
GROUP BY
YEAR(StartDate),
MONTH(StartDate)
)
SELECT
YEAR(m.thisMonth) AS year,
MONTH(m.thisMonth) AS month,
ISNULL(d.EmployeeStartet, 0) AS EmployeeStartet
FROM
months m
LEFT OUTER JOIN data d ON d.year = YEAR(m.thisMonth)
AND d.month = MONTH(m.thisMonth)
ORDER BY
m.thisMonth ASC;

Try
declare #thismonth1 as Date = DateAdd(d, 1 - DatePart(d, CURRENT_TIMESTAMP), CURRENT_TIMESTAMP);
declare #lastMonth1 as Date = DateAdd(d, 1 - DatePart(d, CURRENT_TIMESTAMP), CURRENT_TIMESTAMP);
declare #firstMonth1 as Date = DateAdd(m, -4, #lastMonth1);
select #thismonth1, #lastMonth1, #firstMonth1;
This gives you
#thismonth1
#lastMonth1
#firstMonth1
2021-06-01
2021-06-01
2021-02-01
Correct #lastMonth1 and your query will run just fine. You can use EOMONTH for this.

Build the calendar table for current year including weeknum divided to semester

for the below query i need divide the semesters starting from 1 to 26 .. first semester as 1 to 26 weeks and first semester should start from again 1 to 26
Any help is greating appreciated
DECLARE #StartDate DATETIME
DECLARE #CutoffDate DATETIME
SET #StartDate = Dateadd(yy, Datediff(yy, 0, Getdate()), 0)
SET #CutoffDate = Dateadd(yy, Datediff(yy, 0, Getdate()) + 1, -1)
SELECT day,
[week nu],
semester,
[semester week nu]
INTO #currentdates
FROM (SELECT Day = Dateadd(day, rn - 1, #StartDate),
Datepart(week, Dateadd(day, rn - 1, #StartDate)) [Week nu],
CASE
WHEN Month(Dateadd(day, rn - 1, #StartDate)) <= 6 THEN
'First Semester'
ELSE 'Second Semester'
END AS Semester,
Datepart(week, Dateadd(day, rn - 1, #StartDate)) AS
[Semester Week nu]
FROM (SELECT TOP (Datediff(day, #StartDate, #CutoffDate)) rn =
Row_number()
OVER (
ORDER BY s1.[object_id])
FROM sys.all_objects AS s1
CROSS JOIN sys.all_objects AS s2
ORDER BY s1.[object_id]) AS x) AS y;

I've got a couple of changes, first, you need to add 1 to your last datediff, your last date was December 30, not 31!
Second of all, I just get the date and week number in the first subselect, and then use these ine case statements for the select
The semester number is if week nu<=26,
The semester week nu is week nu if week nu<=26 else wwek nu -26
DECLARE #StartDate datetime DECLARE #CutoffDate datetime
SET #StartDate = DATEADD(yy, DATEDIFF(yy, 0, GETDATE()), 0)
SET #CutoffDate = DATEADD(yy, DATEDIFF(yy, 0, GETDATE()) + 1, -1)
SELECT DAY,
[Week nu],
case when [Week nu]<=26 then 'First Semester' Else 'Second Semester' end Semester,
case when [Week nu]<=26 then [Week nu] Else [Week nu]-26 end[Semester Week nu]
INTO #currentDates
FROM
(SELECT DAY = DATEADD(DAY, rn - 1, #StartDate),
DATEPART(WEEK,DATEADD(DAY, rn - 1, #StartDate)) [Week nu]
FROM
(SELECT TOP (DATEDIFF(DAY, #StartDate, #CutoffDate)+1) rn = ROW_NUMBER() OVER (ORDER BY s1.[object_id])
FROM sys.all_objects AS s1
CROSS JOIN sys.all_objects AS s2
ORDER BY s1.[object_id]) AS x) AS y;

Understanding TSQL Coalesce function

I am trying to select all 12 months / year. And I thought following TSQL code would do this. However, this does not include all months like I want. What is the cause of this? This is modified code:
DECLARE #END_YEAR VARCHAR(10)
DECLARE #END_MONTH VARCHAR(10)
SET #END_YEAR = '2010'
SET #END_MONTH = '10'
DECLARE #TheMonthLastDate DATETIME
DECLARE #TempDate DATETIME
SET #TempDate = '2010-11-01 00:00:00.000'
SET #TheMonthLastDate = '2010-11-01 00:00:00.000'
;with months
as
(
select dateadd(month, -1, dateadd(day, datediff(day, 0, #TempDate), 0)) as m
union all
select dateadd(month, -1, m)
from months
where m > dateadd(month, -12, #TempDate)
)
,yourTable(DateOpened, DateClosed)
as
(select TSK_START_DATE, BTK_CLOSED_DATE
FROM [PROC].ALL_AUDIT
WHERE
(BTK_CLOSED_DATE < #TheMonthLastDate OR
TSK_START_DATE < #TheMonthLastDate
)
)
select yt.DateClosed 'r2', m.m 'r3',
month(coalesce(yt.DateClosed, m.m)) as 'MonthClosed',
year(coalesce(yt.DateClosed, m.m)) as 'YearClosed'
from months m
left join yourTable yt
on
( datepart(year, yt.DateClosed) = DATEPART(year, m.m)
and datepart(month, yt.DateClosed) = DATEPART(month, m.m)
or
datepart(year, yt.DateOpened) = DATEPART(year, m.m)
and datepart(month, yt.DateOpened) = DATEPART(month, m.m)
)
AND year(coalesce(yt.DateClosed, m.m)) = 2010
order by yt.DateClosed
So above query does not return all months. But if I change above WHERE lines to:
FROM [PROC].ALL_AUDIT
WHERE
BTK_CLOSED_DATE < #TheMonthLastDate
then this query does return all 12 months. How can this be?
Output that I want and that I see when WHERE is BTK_CLOSED_DATE < #TheMonthLastDate:
r2 r3 MonthClosed YearClosed
NULL 2010-06-01 00:00:00.000 6 2010
NULL 2009-11-01 00:00:00.000 11 2009
2010-01-06 20:02:19.127 2010-01-01 00:00:00.000 1 2010
2010-01-27 23:13:45.570 2010-01-01 00:00:00.000 1 2010
2010-02-15 14:49:14.427 2010-02-01 00:00:00.000 2 2010
2010-02-15 14:49:14.427 2009-12-01 00:00:00.000 2 2010
But if I instead use WHERE:
(BTK_CLOSED_DATE < #TheMonthLastDate OR
TSK_START_DATE < #TheMonthLastDate
)
then I see:
r2 r3 MonthClosed YearClosed
NULL 2010-10-01 00:00:00.000 10 2010
NULL 2010-09-01 00:00:00.000 9 2010
NULL 2010-09-01 00:00:00.000 9 2010
NULL 2010-08-01 00:00:00.000 8 2010
NULL 2010-08-01 00:00:00.000 8 2010
...
So notice that in first result I see NULL for June 2010, which is what I want.
I think the problem has something to do with the fact that my data contains 2009-2011 data, but I only compare months and not years. How would I add in this additional logic?

The only place where you are reducing the data is with the WHERE clause you have already identified. Therefore, the reason you are not getting all the months you expect is down to the column TSK_START_DATE not being less than #TheMonthLastDate for all months.
To prove this hypothesis, run the following section of your query (I have commented out part of the where clause and removed everything under 'yourTable' cte). The results should show you what is being returned in the TSK_Start_Date column for your missing months and help you identify why the rows are missing when applying the < #TheMonthLastDate clause.
DECLARE #END_YEAR VARCHAR(10)
DECLARE #END_MONTH VARCHAR(10)
SET #END_YEAR = '2010'
SET #END_MONTH = '10'
DECLARE #TheMonthLastDate DATETIME
DECLARE #TempDate DATETIME
SET #TempDate = '2010-11-01 00:00:00.000'
SET #TheMonthLastDate = '2010-11-01 00:00:00.000'
;with months
as
(
select dateadd(month, -1, dateadd(day, datediff(day, 0, #TempDate), 0)) as m
union all
select dateadd(month, -1, m)
from months
where m > dateadd(month, -12, #TempDate)
)
,yourTable(DateOpened, DateClosed)
as
(select TSK_START_DATE, BTK_CLOSED_DATE
FROM [PROC].ALL_AUDIT
WHERE
(BTK_CLOSED_DATE < #TheMonthLastDate OR
--TSK_START_DATE < #TheMonthLastDate
)
)
select * , #TheMonthLastDate TheMonthLastDate from yourTable

How do you calculate the number of weeks between two dates?

How do you calculate the number of weeks between two dates?
for example as follows
Declare #StartDate as DateTime = "01 Jan 2009";
Declare #EndDate as DateTime = "01 June 2009";
#StartDate and #EndDate

Use the Datediff function. datediff(ww,#startdate,#enddate)
the ww tells the function what units you require the difference to be counted in.
http://msdn.microsoft.com/en-us/library/ms189794.aspx

You may use the following function to retrives week's between two dates:
CREATE FUNCTION [dbo].[fGetWeeksList]
(
#StartDate DATETIME
,#EndDate DATETIME
)
RETURNS
TABLE
AS
RETURN
(
SELECT DATEADD(DAY,-(DATEPART(DW,DATEADD(WEEK, x.number, #StartDate))-2),DATEADD(WEEK, x.number, #StartDate)) as [StartDate]
,DATEADD(DAY,-(DATEPART(DW,DATEADD(WEEK, x.number + 1, #StartDate))-1) ,DATEADD(WEEK, x.number + 1, #StartDate)) AS [EndDate]
FROM master.dbo.spt_values x
WHERE x.type = 'P' AND x.number <= DATEDIFF(WEEK, #StartDate, DATEADD(WEEK,0,CAST(#EndDate AS DATE)))

How to calculate age in T-SQL with years, months, and days

What would be the best way to calculate someone's age in years, months, and days in T-SQL (SQL Server 2000)?
The datediff function doesn't handle year boundaries well, plus getting the months and days separate will be a bear. I know I can do it on the client side relatively easily, but I'd like to have it done in my stored procedure.

Here is some T-SQL that gives you the number of years, months, and days since the day specified in #date. It takes into account the fact that DATEDIFF() computes the difference without considering what month or day it is (so the month diff between 8/31 and 9/1 is 1 month) and handles that with a case statement that decrements the result where appropriate.
DECLARE #date datetime, #tmpdate datetime, #years int, #months int, #days int
SELECT #date = '2/29/04'
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 #years, #months, #days

Try this...
SELECT CASE WHEN
(DATEADD(year,DATEDIFF(year, #datestart ,#dateend) , #datestart) > #dateend)
THEN DATEDIFF(year, #datestart ,#dateend) -1
ELSE DATEDIFF(year, #datestart ,#dateend)
END
Basically the "DateDiff( year...", gives you the age the person will turn this year, so i have just add a case statement to say, if they have not had a birthday yet this year, then subtract 1 year, else return the value.

Simple way to get age as text is as below:
Select cast((DATEDIFF(m, date_of_birth, GETDATE())/12) as varchar) + ' Y & ' +
cast((DATEDIFF(m, date_of_birth, GETDATE())%12) as varchar) + ' M' as Age
Results Format will be:
**63 Y & 2 M**

Implemented by arithmetic with ISO formatted date.
declare #now date,#dob date, #now_i int,#dob_i int, #days_in_birth_month int
declare #years int, #months int, #days int
set #now = '2013-02-28'
set #dob = '2012-02-29' -- Date of Birth
set #now_i = convert(varchar(8),#now,112) -- iso formatted: 20130228
set #dob_i = convert(varchar(8),#dob,112) -- iso formatted: 20120229
set #years = ( #now_i - #dob_i)/10000
-- (20130228 - 20120229)/10000 = 0 years
set #months =(1200 + (month(#now)- month(#dob))*100 + day(#now) - day(#dob))/100 %12
-- (1200 + 0228 - 0229)/100 % 12 = 11 months
set #days_in_birth_month = day(dateadd(d,-1,left(convert(varchar(8),dateadd(m,1,#dob),112),6)+'01'))
set #days = (sign(day(#now) - day(#dob))+1)/2 * (day(#now) - day(#dob))
+ (sign(day(#dob) - day(#now))+1)/2 * (#days_in_birth_month - day(#dob) + day(#now))
-- ( (-1+1)/2*(28 - 29) + (1+1)/2*(29 - 29 + 28))
-- Explain: if the days of now is bigger than the days of birth, then diff the two days
-- else add the days of now and the distance from the date of birth to the end of the birth month
select #years,#months,#days -- 0, 11, 28
Test Cases
The approach of days is different from the accepted answer, the differences shown in the comments below:
dob now years months days
2012-02-29 2013-02-28 0 11 28 --Days will be 30 if calculated by the approach in accepted answer.
2012-02-29 2016-02-28 3 11 28 --Days will be 31 if calculated by the approach in accepted answer, since the day of birth will be changed to 28 from 29 after dateadd by years.
2012-02-29 2016-03-31 4 1 2
2012-01-30 2016-02-29 4 0 30
2012-01-30 2016-03-01 4 1 2 --Days will be 1 if calculated by the approach in accepted answer, since the day of birth will be changed to 30 from 29 after dateadd by years.
2011-12-30 2016-02-29 4 1 30
An short version of Days by case statement:
set #days = CASE WHEN day(#now) >= day(#dob) THEN day(#now) - day(#dob)
ELSE #days_in_birth_month - day(#dob) + day(#now) END
If you want the age of years and months only, it could be simpler
set #years = ( #now_i/100 - #dob_i/100)/100
set #months =(12 + month(#now) - month(#dob))%12
select #years,#months -- 1, 0
NOTE: A very useful link of SQL Server Date Formats

Here is a (slightly) simpler version:
CREATE PROCEDURE dbo.CalculateAge
#dayOfBirth datetime
AS
DECLARE #today datetime, #thisYearBirthDay datetime
DECLARE #years int, #months int, #days int
SELECT #today = GETDATE()
SELECT #thisYearBirthDay = DATEADD(year, DATEDIFF(year, #dayOfBirth, #today), #dayOfBirth)
SELECT #years = DATEDIFF(year, #dayOfBirth, #today) - (CASE WHEN #thisYearBirthDay > #today THEN 1 ELSE 0 END)
SELECT #months = MONTH(#today - #thisYearBirthDay) - 1
SELECT #days = DAY(#today - #thisYearBirthDay) - 1
SELECT #years, #months, #days
GO

The same sort of thing as a function.
create function [dbo].[Age](#dayOfBirth datetime, #today datetime)
RETURNS varchar(100)
AS
Begin
DECLARE #thisYearBirthDay datetime
DECLARE #years int, #months int, #days int
set #thisYearBirthDay = DATEADD(year, DATEDIFF(year, #dayOfBirth, #today), #dayOfBirth)
set #years = DATEDIFF(year, #dayOfBirth, #today) - (CASE WHEN #thisYearBirthDay > #today THEN 1 ELSE 0 END)
set #months = MONTH(#today - #thisYearBirthDay) - 1
set #days = DAY(#today - #thisYearBirthDay) - 1
return cast(#years as varchar(2)) + ' years,' + cast(#months as varchar(2)) + ' months,' + cast(#days as varchar(3)) + ' days'
end

create procedure getDatedifference
(
#startdate datetime,
#enddate datetime
)
as
begin
declare #monthToShow int
declare #dayToShow int
--set #startdate='01/21/1934'
--set #enddate=getdate()
if (DAY(#startdate) > DAY(#enddate))
begin
set #dayToShow=0
if (month(#startdate) > month(#enddate))
begin
set #monthToShow= (12-month(#startdate)+ month(#enddate)-1)
end
else if (month(#startdate) < month(#enddate))
begin
set #monthToShow= ((month(#enddate)-month(#startdate))-1)
end
else
begin
set #monthToShow= 11
end
-- set #monthToShow= convert(int, DATEDIFF(mm,0,DATEADD(dd,DATEDIFF(dd,0,#enddate)- DATEDIFF(dd,0,#startdate),0)))-((convert(int,FLOOR(DATEDIFF(day, #startdate, #enddate) / 365.25))*12))-1
if(#monthToShow<0)
begin
set #monthToShow=0
end
declare #amonthbefore integer
set #amonthbefore=Month(#enddate)-1
if(#amonthbefore=0)
begin
set #amonthbefore=12
end
if (#amonthbefore in(1,3,5,7,8,10,12))
begin
set #dayToShow=31-DAY(#startdate)+DAY(#enddate)
end
if (#amonthbefore=2)
begin
IF (YEAR( #enddate ) % 4 = 0 AND YEAR( #enddate ) % 100 != 0) OR YEAR( #enddate ) % 400 = 0
begin
set #dayToShow=29-DAY(#startdate)+DAY(#enddate)
end
else
begin
set #dayToShow=28-DAY(#startdate)+DAY(#enddate)
end
end
if (#amonthbefore in (4,6,9,11))
begin
set #dayToShow=30-DAY(#startdate)+DAY(#enddate)
end
end
else
begin
--set #monthToShow=convert(int, DATEDIFF(mm,0,DATEADD(dd,DATEDIFF(dd,0,#enddate)- DATEDIFF(dd,0,#startdate),0)))-((convert(int,FLOOR(DATEDIFF(day, #startdate, #enddate) / 365.25))*12))
if (month(#enddate)< month(#startdate))
begin
set #monthToShow=12+(month(#enddate)-month(#startdate))
end
else
begin
set #monthToShow= (month(#enddate)-month(#startdate))
end
set #dayToShow=DAY(#enddate)-DAY(#startdate)
end
SELECT
FLOOR(DATEDIFF(day, #startdate, #enddate) / 365.25) as [yearToShow],
#monthToShow as monthToShow ,#dayToShow as dayToShow ,
convert(varchar,FLOOR(DATEDIFF(day, #startdate, #enddate) / 365.25)) +' Year ' + convert(varchar,#monthToShow) +' months '+convert(varchar,#dayToShow)+' days ' as age
return
end

I use this Function I modified (the Days part) From #Dane answer: https://stackoverflow.com/a/57720/2097023
CREATE FUNCTION dbo.EdadAMD
(
#FECHA DATETIME
)
RETURNS NVARCHAR(10)
AS
BEGIN
DECLARE
#tmpdate DATETIME
, #years INT
, #months INT
, #days INT
, #EdadAMD NVARCHAR(10);
SELECT #tmpdate = #FECHA;
SELECT #years = DATEDIFF(yy, #tmpdate, GETDATE()) - CASE
WHEN (MONTH(#FECHA) > MONTH(GETDATE()))
OR (
MONTH(#FECHA) = MONTH(GETDATE())
AND DAY(#FECHA) > DAY(GETDATE())
) THEN
1
ELSE
0
END;
SELECT #tmpdate = DATEADD(yy, #years, #tmpdate);
SELECT #months = DATEDIFF(m, #tmpdate, GETDATE()) - CASE
WHEN DAY(#FECHA) > DAY(GETDATE()) THEN
1
ELSE
0
END;
SELECT #tmpdate = DATEADD(m, #months, #tmpdate);
IF MONTH(#FECHA) = MONTH(GETDATE())
AND DAY(#FECHA) > DAY(GETDATE())
SELECT #days =
DAY(EOMONTH(GETDATE(), -1)) - (DAY(#FECHA) - DAY(GETDATE()));
ELSE
SELECT #days = DATEDIFF(d, #tmpdate, GETDATE());
SELECT #EdadAMD = CONCAT(#years, 'a', #months, 'm', #days, 'd');
RETURN #EdadAMD;
END;
GO
It works pretty well.

I've seen the question several times with results outputting Years, Month, Days but never a numeric / decimal result. (At least not one that doesn't round incorrectly).
I welcome feedback on this function. Might not still need a little adjusting.
-- Input to the function is two dates.
-- Output is the numeric number of years between the two dates in Decimal(7,4) format.
-- Output is always always a possitive number.
-- NOTE:Output does not handle if difference is greater than 999.9999
-- Logic is based on three steps.
-- 1) Is the difference less than 1 year (0.5000, 0.3333, 0.6667, ect.)
-- 2) Is the difference exactly a whole number of years (1,2,3, ect.)
-- 3) (Else)...The difference is years and some number of days. (1.5000, 2.3333, 7.6667, ect.)
CREATE Function [dbo].[F_Get_Actual_Age](#pi_date1 datetime,#pi_date2 datetime)
RETURNS Numeric(7,4)
AS
BEGIN
Declare
#l_tmp_date DATETIME
,#l_days1 DECIMAL(9,6)
,#l_days2 DECIMAL(9,6)
,#l_result DECIMAL(10,6)
,#l_years DECIMAL(7,4)
--Check to make sure there is a date for both inputs
IF #pi_date1 IS NOT NULL and #pi_date2 IS NOT NULL
BEGIN
IF #pi_date1 > #pi_date2 --Make sure the "older" date is in #pi_date1
BEGIN
SET #l_tmp_date = #pi_date2
SET #pi_date2 = #Pi_date1
SET #pi_date1 = #l_tmp_date
END
--Check #1 If date1 + 1 year is greater than date2, difference must be less than 1 year
IF DATEADD(YYYY,1,#pi_date1) > #pi_date2
BEGIN
--How many days between the two dates (numerator)
SET #l_days1 = DATEDIFF(dd,#pi_date1, #pi_date2)
--subtract 1 year from date2 and calculate days bewteen it and date2
--This is to get the denominator and accounts for leap year (365 or 366 days)
SET #l_days2 = DATEDIFF(dd,dateadd(yyyy,-1,#pi_date2),#pi_date2)
SET #l_years = #l_days1 / #l_days2 -- Do the math
END
ELSE
--Check #2 Are the dates an exact number of years apart.
--Calculate years bewteen date1 and date2, then add the years to date1, compare dates to see if exactly the same.
IF DATEADD(YYYY,DATEDIFF(YYYY,#pi_date1,#pi_date2),#pi_date1) = #pi_date2
SET #l_years = DATEDIFF(YYYY,#pi_date1, #pi_date2) --AS Years, 'Exactly even Years' AS Msg
ELSE
BEGIN
--Check #3 The rest of the cases.
--Check if datediff, returning years, over or under states the years difference
SET #l_years = DATEDIFF(YYYY,#pi_date1, #pi_date2)
IF DATEADD(YYYY,#l_years,#pi_date1) > #pi_date2
SET #l_years = #l_years -1
--use basicly same logic as in check #1
SET #l_days1 = DATEDIFF(dd,DATEADD(YYYY,#l_years,#pi_date1), #pi_date2)
SET #l_days2 = DATEDIFF(dd,dateadd(yyyy,-1,#pi_date2),#pi_date2)
SET #l_years = #l_years + #l_days1 / #l_days2
--SELECT #l_years AS Years, 'Years Plus' AS Msg
END
END
ELSE
SET #l_years = 0 --If either date was null
RETURN #l_Years --Return the result as decimal(7,4)
END
`

Quite Old question, but I want to share what I have done to calculate age
Declare #BirthDate As DateTime
Set #BirthDate = '1994-11-02'
SELECT DATEDIFF(YEAR,#BirthDate,GETDATE()) - (CASE
WHEN MONTH(#BirthDate)> MONTH(GETDATE()) THEN 1
WHEN MONTH(#BirthDate)= MONTH(GETDATE()) AND DAY(#BirthDate) > DAY(GETDATE()) THEN 1
Else 0 END)

Are you trying to calculate the total days/months/years of an age? do you have a starting date? Or are you trying to dissect it (ex: 24 years, 1 month, 29 days)?
If you have a start date that you're working with, datediff will output the total days/months/years with the following commands:
Select DateDiff(d,'1984-07-12','2008-09-11')
Select DateDiff(m,'1984-07-12','2008-09-11')
Select DateDiff(yyyy,'1984-07-12','2008-09-11')
with the respective outputs being (8827/290/24).
Now, if you wanted to do the dissection method, you'd have to subtract the number of years in days (days - 365*years), and then do further math on that to get the months, etc.

Here is SQL code that gives you the number of years, months, and days since the sysdate.
Enter value for input_birth_date this format(dd_mon_yy). note: input same value(birth date) for years, months & days such as 01-mar-85
select trunc((sysdate -to_date('&input_birth_date_dd_mon_yy'))/365) years,
trunc(mod(( sysdate -to_date('&input_birth_date_dd_mon_yy'))/365,1)*12) months,
trunc((mod((mod((sysdate -to_date('&input_birth_date_dd_mon_yy'))/365,1)*12),1)*30)+1) days
from dual

DateTime values in T-SQL are stored as floats. You can just subtract the dates from each other and you now have a new date that is the timespan between them.
declare #birthdate datetime
set #birthdate = '6/15/1974'
--age in years - short version
print year(getdate() - #birthdate) - year(0)
--age in years - visualization
declare #mindate datetime
declare #span datetime
set #mindate = 0
set #span = getdate() - #birthdate
print #mindate
print #birthdate
print getdate()
print #span
--substract minyear from spanyear to get age in years
print year(#span) - year(#mindate)
print month(#span)
print day(#span)

CREATE FUNCTION DBO.GET_AGE
(
#DATE AS DATETIME
)
RETURNS VARCHAR(MAX)
AS
BEGIN
DECLARE #YEAR AS VARCHAR(50) = ''
DECLARE #MONTH AS VARCHAR(50) = ''
DECLARE #DAYS AS VARCHAR(50) = ''
DECLARE #RESULT AS VARCHAR(MAX) = ''
SET #YEAR = CONVERT(VARCHAR,(SELECT DATEDIFF(MONTH,CASE WHEN DAY(#DATE) > DAY(GETDATE()) THEN DATEADD(MONTH,1,#DATE) ELSE #DATE END,GETDATE()) / 12 ))
SET #MONTH = CONVERT(VARCHAR,(SELECT DATEDIFF(MONTH,CASE WHEN DAY(#DATE) > DAY(GETDATE()) THEN DATEADD(MONTH,1,#DATE) ELSE #DATE END,GETDATE()) % 12 ))
SET #DAYS = DATEDIFF(DD,DATEADD(MM,CONVERT(INT,CONVERT(INT,#YEAR)*12 + CONVERT(INT,#MONTH)),#DATE),GETDATE())
SET #RESULT = (RIGHT('00' + #YEAR, 2) + ' YEARS ' + RIGHT('00' + #MONTH, 2) + ' MONTHS ' + RIGHT('00' + #DAYS, 2) + ' DAYS')
RETURN #RESULT
END
SELECT DBO.GET_AGE('04/12/1986')

DECLARE #BirthDate datetime, #AgeInMonths int
SET #BirthDate = '10/5/1971'
SET #AgeInMonths -- Determine the age in "months old":
= DATEDIFF(MONTH, #BirthDate, GETDATE()) -- .Get the difference in months
- CASE WHEN DATEPART(DAY,GETDATE()) -- .If today was the 1st to 4th,
< DATEPART(DAY,#BirthDate) -- (or before the birth day of month)
THEN 1 ELSE 0 END -- ... don't count the month.
SELECT #AgeInMonths / 12 as AgeYrs -- Divide by 12 months to get the age in years
,#AgeInMonths % 12 as AgeXtraMonths -- Get the remainder of dividing by 12 months = extra months
,DATEDIFF(DAY -- For the extra days, find the difference between,
,DATEADD(MONTH, #AgeInMonths -- 1. Last Monthly Birthday
, #BirthDate) -- (if birthdays were celebrated monthly)
,GETDATE()) as AgeXtraDays -- 2. Today's date.

For the ones that want to create a calculated column in a table to store the age:
CASE WHEN DateOfBirth< DATEADD(YEAR, (DATEPART(YEAR, GETDATE()) - DATEPART(YEAR, DateOfBirth))*-1, GETDATE())
THEN DATEPART(YEAR, GETDATE()) - DATEPART(YEAR, DateOfBirth)
ELSE DATEPART(YEAR, GETDATE()) - DATEPART(YEAR, DateOfBirth) -1 END

There is an easy way, based on the hours between the two days BUT with the end date truncated.
SELECT CAST(DATEDIFF(hour,Birthdate,CAST(GETDATE() as Date))/8766.0 as INT) AS Age FROM <YourTable>
This one has proven to be extremely accurate and reliable. If it weren't for the inner CAST on the GETDATE() it might flip the birthday a few hours before midnight but, with the CAST, it is dead on with the age changing over at exactly midnight.

Here is how I calculate the age given a birth date and the 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

There is another method for calculate age is
See below table
FirstName LastName DOB
sai krishnan 1991-11-04
Harish S A 1998-10-11
For finding age,you can calculate through month
Select datediff(MONTH,DOB,getdate())/12 as dates from [Organization].[Employee]
Result will be
firstname dates
sai 27
Harish 20

I have created a function calculateAge that takes parameter dateOfBirth from outside and then it calculates the age in years, months and days and finally it returns in string format.
CREATE FUNCTION calculateAge(dateOfBirth datetime) RETURNS varchar(40)
BEGIN
set #currentdatetime = CURRENT_TIMESTAMP;
set #years = TIMESTAMPDIFF(YEAR,dateOfBirth,#currentdatetime);
set #months = TIMESTAMPDIFF(MONTH,dateOfBirth,#currentdatetime) - #years*12 ;
set #dayOfBirth = EXTRACT(DAY FROM dateOfBirth);
set #today = EXTRACT(DAY FROM #currentdatetime);
set #days = 0;
if (#today > #dayOfBirth) then
set #days = #today - #dayOfBirth;
else
set #decreaseMonth = DATE_SUB(#currentdatetime, INTERVAL 1 MONTH);
set #days = DATEDIFF(dateOfBirth, #decreaseMonth);
end if;
RETURN concat(concat( concat(#years , "years\n") , concat(#months , "months\n")), concat(#days , "days"));
END

Plenty of solutions have been given already, but I beleive this one to be both easy to understand and reliable, as it will handle leap years as well :
case when datepart(dayofyear, #birth) <= datepart(dayofyear, getdate())
then datepart(year, getdate()) - datepart(year, #birth)
else datepart(year, getdate()) - datepart(year, #birth) - 1
end
The idea is to simply compute the difference in years between the two years (birth and now), and substract 1 if the anniversary has not been reached for the current year.

declare #StartDate datetime = '2016-01-31'
declare #EndDate datetime = '2016-02-01'
SELECT #StartDate AS [StartDate]
,#EndDate AS [EndDate]
,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END AS [Years]
,DATEDIFF(Month,(DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate)),#EndDate) - CASE WHEN DATEADD(Month, DATEDIFF(Month,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate),#EndDate) , #StartDate) > #EndDate THEN 1 ELSE 0 END AS [Months]
,DATEDIFF(Day, DATEADD(Month,DATEDIFF(Month, (DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate)),#EndDate) - CASE WHEN DATEADD(Month, DATEDIFF(Month,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate),#EndDate) , #StartDate) > #EndDate THEN 1 ELSE 0 END ,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate)) ,#EndDate) - CASE WHEN DATEADD(Day,DATEDIFF(Day, DATEADD(Month,DATEDIFF(Month, (DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate)),#EndDate) - CASE WHEN DATEADD(Month, DATEDIFF(Month,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate),#EndDate) , #StartDate) > #EndDate THEN 1 ELSE 0 END ,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate)) ,#EndDate),DATEADD(Month,DATEDIFF(Month, (DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate)),#EndDate) - CASE WHEN DATEADD(Month, DATEDIFF(Month,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate),#EndDate) , #StartDate) > #EndDate THEN 1 ELSE 0 END ,DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate) - CASE WHEN DATEADD(Year,DATEDIFF(Year,#StartDate,#EndDate), #StartDate) > #EndDate THEN 1 ELSE 0 END,#StartDate))) > #EndDate THEN 1 ELSE 0 END AS [Days]

select DOB as Birthdate,
YEAR(GETDATE()) as ThisYear,
YEAR(getdate()) - EAR(date1) as Age
from TableName

SELECT DOB AS Birthdate ,
YEAR(GETDATE()) AS ThisYear,
YEAR(getdate()) - YEAR(DOB) AS Age
FROM tableprincejain

DECLARE #DoB AS DATE = '1968-10-24'
DECLARE #cDate AS DATE = CAST('2000-10-23' AS DATE)
SELECT
--Get Year difference
DATEDIFF(YEAR,#DoB,#cDate) -
--Cases where year difference will be augmented
CASE
--If Date of Birth greater than date passed return 0
WHEN YEAR(#DoB) - YEAR(#cDate) >= 0 THEN DATEDIFF(YEAR,#DoB,#cDate)
--If date of birth month less than date passed subtract one year
WHEN MONTH(#DoB) - MONTH(#cDate) > 0 THEN 1
--If date of birth day less than date passed subtract one year
WHEN MONTH(#DoB) - MONTH(#cDate) = 0 AND DAY(#DoB) - DAY(#cDate) > 0 THEN 1
--All cases passed subtract zero
ELSE 0
END

declare #BirthDate datetime
declare #TotalYear int
declare #TotalMonths int
declare #TotalDays int
declare #TotalWeeks int
declare #TotalHours int
declare #TotalMinute int
declare #TotalSecond int
declare #CurrentDtTime datetime
set #BirthDate='1998/01/05 05:04:00' -- Set Your date here
set #TotalYear= FLOOR(DATEDIFF(DAY, #BirthDate, GETDATE()) / 365.25)
set #TotalMonths= FLOOR(DATEDIFF(DAY,DATEADD(year, #TotalYear,#BirthDate),GetDate()) / 30.436875E)
set #TotalDays= FLOOR(DATEDIFF(DAY, DATEADD(month, #TotalMonths,DATEADD(year,
#TotalYear,#BirthDate)), GETDATE()))
set #CurrentDtTime=CONVERT(datetime,CONVERT(varchar(50), DATEPART(year,
GetDate()))+'/' +CONVERT(varchar(50), DATEPART(MONTH, GetDate()))
+'/'+ CONVERT(varchar(50),DATEPART(DAY, GetDate()))+' '
+ CONVERT(varchar(50),DATEPART(HOUR, #BirthDate))+':'+
CONVERT(varchar(50),DATEPART(MINUTE, #BirthDate))+
':'+ CONVERT(varchar(50),DATEPART(Second, #BirthDate)))
set #TotalHours = DATEDIFF(hour, #CurrentDtTime, GETDATE())
if(#TotalHours < 0)
begin
set #TotalHours = DATEDIFF(hour,DATEADD(Day,-1, #CurrentDtTime), GETDATE())
set #TotalDays= #TotalDays -1
end
set #TotalMinute= DATEPART(MINUTE, GETDATE())-DATEPART(MINUTE, #BirthDate)
if(#TotalMinute < 0)
set #TotalMinute = DATEPART(MINUTE, DATEADD(hour,-1,GETDATE()))+(60-DATEPART(MINUTE,
#BirthDate))
set #TotalSecond= DATEPART(Second, GETDATE())-DATEPART(Second, #BirthDate)
Print 'Your age are'+ CHAR(13)
+ CONVERT(varchar(50), #TotalYear)+' Years, ' +
CONVERT(varchar(50),#TotalMonths) +' Months, ' +
CONVERT(varchar(50),#TotalDays)+' Days, ' +
CONVERT(varchar(50),#TotalHours)+' Hours, ' +
CONVERT(varchar(50),#TotalMinute)+' Minutes, ' +
CONVERT(varchar(50),#TotalSecond)+' Seconds. ' +char(13)+
'Your are born at day of week was - ' + CONVERT(varchar(50),DATENAME(dw ,
#BirthDate ))
+char(13)+char(13)+
+'Your Birthdate to till date your '+ CHAR(13)
+'Years - ' + CONVERT(varchar(50), FLOOR(DATEDIFF(DAY, #BirthDate, GETDATE()) /
365.25))
+' , Months - ' + CONVERT(varchar(50),DATEDIFF(MM,#BirthDate,getdate()))
+' , Weeks - ' + CONVERT(varchar(50),DATEDIFF(wk,#BirthDate,getdate()))
+' , Days - ' + CONVERT(varchar(50),DATEDIFF(dd,#BirthDate,getdate()))+char(13)+
+'Hours - ' + CONVERT(varchar(50),DATEDIFF(HH,#BirthDate,getdate()))
+' , Minutes - ' + CONVERT(varchar(50),DATEDIFF(mi,#BirthDate,getdate()))
+' , Seconds - ' + CONVERT(varchar(50),DATEDIFF(ss,#BirthDate,getdate()))
Output
Your age are
22 Years, 0 Months, 2 Days, 11 Hours, 30 Minutes, 16 Seconds.
Your are born at day of week was - Monday
Your Birthdate to till date your
Years - 22 , Months - 264 , Weeks - 1148 , Days - 8037
Hours - 192899 , Minutes - 11573970 , Seconds - 694438216