If you are after accurate way to calculate Age using T-SQL then the below post might help you.
Below are questions that I try to answer in this post:
T-SQL Date of birth to Age
T-SQL Age Function (UDF)
- There are many example on the web of inaccurate calculation of age or date of birth. Some of them calculate it without taking into consideration month and day of month. Here is a link to one of these pages T-SQL Age (inaccurate) which tries to calculate age by dividing it by 365.25.
Sometimes you might be after just a way to calculate difference in years and below is an example that you can use:
SELECT DATEDIFF(Year,'1983-08-19',GETDATE()) AS AGE -- THIS IS DIFFERENCE IN YEARS
But more ofter you want to calculate precise age and not accurate in 99% of cases but accurate in 100% of cases and below is how you can do that.
If you would like to calcualte person's age using t-sql by converting person's date of birth to age then the below t-sql statement might help you.
-- first we declare date of birth and the date we want to compare it to (usually today's date).
DECLARE @DOB AS DATETIME
SET @DOB = '1983-08-19'
DECLARE @CompareDate AS DATETIME
SET @CompareDate = GETDATE()
-- below is t-sql statement that performs the actual conversion from date of birt to age.
SELECT CASE WHEN (MONTH(@CompareDate)*100)+DAY(@CompareDate) >= (MONTH(@DOB)*100)+DAY(@DOB)
THEN DATEDIFF(Year,@DOB,@CompareDate) ELSE DATEDIFF(Year,@DOB,@CompareDate)-1 END AS Age
-- below example is the same above but based on field from database and getdate()
SELECT CASE WHEN (MONTH(GETDATE())*100)+DAY(GETDATE()) >= (MONTH(DOB_Field)*100)+DAY(DOB_Field)
THEN DATEDIFF(Year,DOB_Field,GETDATE()) ELSE DATEDIFF(Year,DOB_Field,GETDATE())-1 END AS Age
-- and another t-sql statement but based on both dob field from database and comparedate from database as well.
SELECT CASE WHEN (MONTH(CompareDate_Field)*100)+DAY(CompareDate_Field) >= (MONTH(DOB_Field)*100)+DAY(DOB_Field)
THEN DATEDIFF(Year,DOB_Field,CompareDate_Field) ELSE DATEDIFF(Year,DOB_Field,CompareDate_Field)-1 END AS Age
The link provides an alternative calculation T-SQL Age (also accurate)
Below is T-SQL Age Function (UDF) which you can use and modify. Please be aware that it was created using SQL Server 2008 R2 function so it might not work on 2008 or 2005 without version adjustments.
CREATE FUNCTION [dbo].[udfCalculateAge]
@DOB AS DATE,
@EndDate as DATE = '2999-01-01' -- Defaul is today's date (see below) but any date can be used here
DECLARE @Result as TINYINT
-- IF DEFAULT VALUE (marked as 2999-01-01 as it doesn't accept functions) IS USED THEN USE TODAY'S DATE
IF @EndDate = '2999-01-01'
SET @EndDate = GETDATE()
IF @DOB >= @EndDate -- trap errors
SET @Result = 0
-- check if the person had its birthday in the specified year and calculate age
IF (MONTH(@EndDate)*100)+DAY(@EndDate) >= (MONTH(@DOB)*100)+DAY(@DOB)
SET @Result = DATEDIFF(Year,@DOB,@EndDate)
SET @Result = DATEDIFF(Year,@DOB,@EndDate)-1
Hope that helps!