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

Question

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

Answer 1

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