Calculating age in a certain month in SQL Server - sql

Question

I need to extraxt a list of users who turn 15 years old in any day in a certain month (e.g. in June or in July) and I am trying to use string comparison in SQL Server (stored procedure) but it is not working.
I get #Month parameter from a SSRS which is given from a dropdown list of next 10 months. (some of this month will be in the next year).
I have an Age function which converts a date format from 27/07/2003 (BirthDate) to a string 15 years,2 months,27 days. Naturally, There are people aged 9 years, 0 months, 2 days as well.
So far, I could write the code to check if the person will be 15 and at least 1 month (15 years,1 months) in next July (#Month + 1) supposing we want to know if they turn 15 in June (#Month) but still it is not working because of string comparison.
Age(BirthDate, GETDATE()) is the function which turns age in this format:
15 years,2 months,27 days as string.
I hope it is clear what I mean.
declare #Age varchar (20) = 15,
#Month varchar (25) = 'June',
#CurrentMonth varchar (20) = null,
SET #CurrentMonth = DATENAME(month, GETDATE()); /* returns current month in string */
SELECT My_ID
,Title
,FirstName
,LastName
,Gender
,CONVERT(VARCHAR, BirthDate, 103) AS BirthDate
,dbo.Age(BirthDate, GETDATE()) AS Age
,LocalityName AS Locality
,GETDATE() AS ReportDate
,MONTH(GETDATE()) AS MONTH
,YEAR(GETDATE()) AS YEAR
FROM dbo.vw_individuals
WHERE (LEFT(dbo.Age(BirthDate, DATEADD(month, 1 +
(SELECT DATEDIFF(MONTH, #CurrentMonth + ' 01 2010', #Month + ' 01 2010')
+ CASE WHEN DATEDIFF(MONTH, #CurrentMonth + ' 01 2010', #Month + ' 01 2010') < 0 THEN 12 ELSE 0 END)
, GETDATE())), 2) = #Age)
AND (LEFT(dbo.Age(BirthDate, DATEADD(month, 1 +
(SELECT DATEDIFF(MONTH, #CurrentMonth + ' 01 2010', #Month + ' 01 2010')
+ CASE WHEN DATEDIFF(MONTH, #CurrentMonth + ' 01 2010', #Month + ' 01 2010') < 0 THEN 12 ELSE 0 END)
, GETDATE())), 16) < #Age + ' years,2 month')
AND (month(convert(DATETIME, BirthDate, 103)) = (SELECT DATEPART(MM, #Month + '01 2010'))) /* Checks if the BirthDate month is the same as the chosen month (#Month) */

Answer 1

so given the #Month and #Year you're interested in, then the people you need are given BY
SELECT ..... WHERE YEAR(BirthDate) = #YEAR - 15 AND Month(BirthDate) = #Month
so all the people returned have a 15th birthday in #Month/#Year
-- bit of a pain though, might not quite work if a person is born 29th February, they turn 15 in March although that will never be a leap year, so you could get away with
SELECT ..... WHERE YEAR(BirthDate) = #YEAR - 15
AND Month(BirthDate)
+ CASE WHEN MONTH(Birthdate) = 2 AND DAY(Birthdate) = 29 THEN 1 ELSE 0 END
= #Month

Answer 2

Below should show you way to go, your query is much too complicated for what you need (I think), just use logic from my IF in your WHERE
declare #dob datetime = '2003-10-13 17:21:45.620'
if(month(#dob) = month(getdate())
AND year(#dob)+15 = year(getdate()))
print '15 years old this month'
else
print 'not 15 years old this month'
The same yoke, just used table variable:
declare #dob datetime = '2003-10-13 17:21:45.620'
declare #t table (dob datetime)
insert into #t
values ('2003-10-13 17:21:45.620'), ('2004-10-13 17:21:45.620'), ('2003-10-30 17:21:45.620')
select *
from #t
where month(dob) = month(getdate())
and year(dob)+15 = year(getdate())
EDIT
Other way to achieve what you need is to use DATEDIFF
declare #dob datetime = '2003-10-13 17:21:45.620'
declare #t table (dob datetime)
insert into #t
values ('2003-10-13 17:21:45.620'),
('2004-10-13 17:21:45.620'),
('2003-10-30 17:21:45.620')
select *
from #t
where datediff(month, dob, getdate()) = 180 --(15 years * 12months)