T-SQL: calculate age then add character to result - sql

Question

Been stuck on this one for a while now. Let's say I have a Client table like the one here:
Name BirthDayNum BirthMonthNum BirthYearNum
--------------------------------------------------
John 23 12 1965
Jane 4 9 1975
Joe 6 3 1953
Currently I am calculating the age using this syntax: (sorry if it is hard to read)
DATEDIFF(year, CONVERT(datetime, CAST(client.BirthMonthNum AS varchar(2))
+ '-' + CAST(client.BirthDayNum AS varchar(2))
+ '-' + CAST(client.BirthYearNum AS varchar(4)), 101), GETDATE())
- (CASE WHEN dateadd(YY, DATEDIFF(year, CONVERT(datetime, CAST(client.BirthMonthNum AS varchar(2))
+ '-' + CAST(client.BirthDayNum AS varchar(2))
+ '-' + CAST(client.BirthYearNum AS varchar(4)), 101), GETDATE()),
CONVERT(datetime, CAST(client.BirthMonthNum AS varchar(2))
+ '-' + CAST(client.BirthDayNum AS varchar(2))
+ '-' + CAST(client.BirthYearNum AS varchar(4)), 101)) > getdate() THEN 1 ELSE 0 END) AS 'Client Age'
This will give me the age in years. Of course if I want months, I just change the DATEDIFF(year to month. So, what I am trying to do now is this.
Continue to calculate the age, but instead of returning either years or months, I would like to return the age in years and months, but also, concat a 'y' and 'm' within the value as well. Ex. 41y 11m for Jane above.
So basically I am trying to figure out how to add a char to the return value, as well as calculate the remaining months beyond the year calculation.
Any help would be greatly appreciated!

Answer 1

Tired of twisting myself into knots with date calculations, I created a Table-Valued-Function to calculate elapsed time in Years, Months, Days, Hours, Minutes, and Seconds.
Example
Declare #YourTable table (Name varchar(50),BirthDayNum int, BirthMonthNum int, BirthYearNum int)
Insert Into #YourTable values
('John', 23, 12, 1965),
('Jane', 4, 9, 1975),
('Joe', 6, 3, 1953)
Select A.Name
,B.*
,Age = concat(C.Years,'y ',C.Months,'m')
From #YourTable A
Cross Apply (Select DOB = DateFromParts(A.BirthYearNum,A.BirthMonthNum,A.BirthDayNum)) B
Cross Apply [dbo].[udf-Date-Elapsed](B.DOB,GetDate()) C
Returns
Name DOB Age
John 1965-12-23 51y 3m
Jane 1975-09-04 41y 6m
Joe 1953-03-06 64y 0m
The UDF - May look like overkill, but it is very performant
CREATE FUNCTION [dbo].[udf-Date-Elapsed] (#D1 DateTime,#D2 DateTime)
Returns Table
Return (
with cteBN(N) as (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
cteRN(R) as (Select Row_Number() Over (Order By (Select NULL))-1 From cteBN a,cteBN b,cteBN c),
cteYY(N,D) as (Select Max(R),Max(DateAdd(YY,R,#D1))From cteRN R Where DateAdd(YY,R,#D1)<=#D2),
cteMM(N,D) as (Select Max(R),Max(DateAdd(MM,R,D)) From (Select Top 12 R From cteRN Order By 1) R, cteYY P Where DateAdd(MM,R,D)<=#D2),
cteDD(N,D) as (Select Max(R),Max(DateAdd(DD,R,D)) From (Select Top 31 R From cteRN Order By 1) R, cteMM P Where DateAdd(DD,R,D)<=#D2),
cteHH(N,D) as (Select Max(R),Max(DateAdd(HH,R,D)) From (Select Top 24 R From cteRN Order By 1) R, cteDD P Where DateAdd(HH,R,D)<=#D2),
cteMI(N,D) as (Select Max(R),Max(DateAdd(MI,R,D)) From (Select Top 60 R From cteRN Order By 1) R, cteHH P Where DateAdd(MI,R,D)<=#D2),
cteSS(N,D) as (Select Max(R),Max(DateAdd(SS,R,D)) From (Select Top 60 R From cteRN Order By 1) R, cteMI P Where DateAdd(SS,R,D)<=#D2)
Select [Years] = cteYY.N
,[Months] = cteMM.N
,[Days] = cteDD.N
,[Hours] = cteHH.N
,[Minutes] = cteMI.N
,[Seconds] = cteSS.N
From cteYY,cteMM,cteDD,cteHH,cteMI,cteSS
)
--Max 1000 years
--Select * from [dbo].[udf-Date-Elapsed] ('1991-09-12 21:00:00.000',GetDate())
Just to Illustrate
The TVF without any secondary string manipulation would return
Select A.Name
,B.*
From #YourTable A
Cross Apply [dbo].[udf-Date-Elapsed](DateFromParts(A.BirthYearNum,A.BirthMonthNum,A.BirthDayNum),GetDate()) B
EDIT - READ ONLY VERSION
Select A.Name
,B.*
,Age = concat(DateDiff(MONTH,B.DOB,GetDate())/12,'y ',DateDiff(MONTH,B.DOB,GetDate()) % 12,'m')
From #YourTable A
Cross Apply (Select DOB = DateFromParts(A.BirthYearNum,A.BirthMonthNum,A.BirthDayNum)) B

Answer 2

Yes it is easier to save as DOB.. But one simple method
select concat( floor(datediff(year, datefromparts(birthyearnum,birthmonthnum,birthdaynum), getdate()))-1, 'y ', datediff(month, datefromparts(birthyearnum,birthmonthnum,birthdaynum), getdate())%12, 'm')
from #yourDates
How age for 1965 is 41y?
Input table:
create table #yourdates(Name varchar(10), BirthdayNum int, BirthMonthNum int, BirthYearNum int)
insert into #yourdates
(Name, BirthdayNum, BirthMonthNum, BirthYearNum) values
('John', 23 , 12 , 1965 )
,('Jane', 4 , 9 , 1975 )
,('Joe ', 6 , 3 , 1953 )

Answer 3

If you are on 2008 or lesser and can't use datefromparts...
declare #table table ([Name] varchar(4), BirthDayNum int, BirthMonthNum int, BirthYearNum int)
insert into #table
values
('John',23,12,1965),
('Jane',4,9,1975),
('Day',30,3,1990)
;with cte as(
select
[Name],
cast(BirthYearNum as varchar(4)) + '/' + cast(BirthMonthNum as varchar(2)) + '/' + cast(BirthDayNum as varchar(2)) as DOB
from
#table)
select
[Name]
,DOB
,datediff(year,DOB,GETDATE()) as Years
,datediff(month,DOB,GETDATE()) %12 as Months
,rtrim(cast(datediff(year,DOB,GETDATE()) as char(2))) + 'y ' + rtrim(cast(datediff(month,DOB,GETDATE()) %12 as char(2))) + 'm' as Age
from cte