Finding someone's age in SQL

Question

In a SQL Server database, I record people\'s date of birth. Is there an straight-forward method of working out the person\'s age on a given date using SQL only?

Usi

Answer 1

I hope this one is perfect provided you accept the algorithm that a leap-baby turns a year older on successive February 29th's, or March 1's on non-leap years. @DOB must contain a date within a few centuries of now, @AsOf must contain a similar date >= @DOB:

SET @Age = YEAR(@AsOf) - YEAR(@DOB) - 1
IF MONTH(@AsOf) * 100 + DAY(@AsOf) >= MONTH(@DOB) * 100 + DAY(@DOB)
    SET @Age = @Age + 1

I'd REALLY REALLY appreciate any testing and comments as I haven't found a way yet to break it... yet.

Added - 1/31/2014: This one seems to work perfectly too even though at first glance it looks too crude:

SET @Age = FLOOR(DATEDIFF(dd,@DOB,@CompareDate)/365.25)

Pop these in a function and here's a test script:

    SELECT dbo.fnGetAge('2/27/2008', '2/27/2012')
    SELECT dbo.fnGetAge('2/27/2008', '2/28/2012')
    SELECT dbo.fnGetAge('2/27/2008', '2/29/2012')
    SELECT dbo.fnGetAge('2/27/2008', '3/1/2012')
    -- 4 4 4 4
    SELECT dbo.fnGetAge('2/28/2008', '2/27/2012')
    SELECT dbo.fnGetAge('2/28/2008', '2/28/2012')
    SELECT dbo.fnGetAge('2/28/2008', '2/29/2012')
    SELECT dbo.fnGetAge('2/28/2008', '3/1/2012')
    -- 3 4 4 4
    SELECT dbo.fnGetAge('2/29/2008', '2/27/2012')
    SELECT dbo.fnGetAge('2/29/2008', '2/28/2012')
    SELECT dbo.fnGetAge('2/29/2008', '2/29/2012')
    SELECT dbo.fnGetAge('2/29/2008', '3/1/2012')
    -- 3 3 4 4
    SELECT dbo.fnGetAge('3/1/2008', '2/27/2012')
    SELECT dbo.fnGetAge('3/1/2008', '2/28/2012')
    SELECT dbo.fnGetAge('3/1/2008', '2/29/2012')
    SELECT dbo.fnGetAge('3/1/2008', '3/1/2012')
    -- 3 3 3 4
    SELECT dbo.fnGetAge('3/1/2007', '2/27/2012')
    SELECT dbo.fnGetAge('3/1/2007', '2/28/2012')
    SELECT dbo.fnGetAge('3/1/2007', '2/29/2012')
    SELECT dbo.fnGetAge('3/1/2007', '3/1/2012')
    -- 4 4 4 5
    SELECT dbo.fnGetAge('3/1/2007', '2/27/2013')
    SELECT dbo.fnGetAge('3/1/2007', '2/28/2013')
    SELECT dbo.fnGetAge('3/1/2007', '3/1/2013')
    SELECT dbo.fnGetAge('2/27/2007', '2/28/2013')
    SELECT dbo.fnGetAge('2/28/2007', '2/28/2014')
    -- 5 5 6 6 7

Cheers

PS: You can probably tweak the February 29 decision to being a day earlier if that floats your boat.