SQL Select Upcoming Birthdays

Liked the approach of @strelc, but his sql was a bit off. Here's an updated version that works well and is simple to use:

SELECT * FROM User 
WHERE (DATEDIFF(dd, getdate(), DATEADD(yyyy, 
    DATEDIFF(yyyy, birthdate, getdate()) + 1, birthdate)) + 1) % 366 <= <number of days>

edit 10/2017: add single day to end

Best use of datediff and dateadd. No rounding, no approximates, no 29th of february bug, nothing but date functions

1. ageOfThePerson = DATEDIFF(yyyy,dateOfBirth, GETDATE())

2. dateOfNextBirthday = DATEADD(yyyy,ageOfThePerson + 1, dateOfBirth)

3. daysBeforeBirthday = DATEDIFF(d,GETDATE(), dateofNextBirthday)

Thanks to @Gustavo Cardoso, new definition for the age of the person

1. ageOfThePerson = FLOOR(DATEDIFF(d,dateOfBirth, GETDATE())/365.25)

In case someone is still looking for a solution in MySQL (slightly different commands), here's the query:

SELECT
 name,birthday,
 FLOOR(DATEDIFF(DATE(NOW()),birthday) / 365.25) AS age_now,
 FLOOR(DATEDIFF(DATE_ADD(DATE(NOW()),INTERVAL 30 DAY),birthday) / 365.25) AS age_future

FROM user

WHERE 1 = (FLOOR(DATEDIFF(DATE_ADD(DATE(NOW()),INTERVAL 30 DAY),birthday) / 365.25)) - (FLOOR(DATEDIFF(DATE(NOW()),birthday) / 365.25))

ORDER BY MONTH(birthday),DAY(birthday)

Note: I've edited this to fix what I believe was a significant bug. The currently posted version works for me.

This should work after you modify the field and table names to correspond to your database.

SELECT 
  BRTHDATE AS BIRTHDAY
 ,FLOOR(DATEDIFF(dd,EMP.BRTHDATE,GETDATE()) / 365.25) AS AGE_NOW
 ,FLOOR(DATEDIFF(dd,EMP.BRTHDATE,GETDATE()+7) / 365.25) AS AGE_ONE_WEEK_FROM_NOW
FROM 
  "Database name".dbo.EMPLOYEES EMP
WHERE 1 = (FLOOR(DATEDIFF(dd,EMP.BRTHDATE,GETDATE()+7) / 365.25))
          -
          (FLOOR(DATEDIFF(dd,EMP.BRTHDATE,GETDATE()) / 365.25))

Basically, it gets the # of days from their birthday to now, and divides that by 365 (to avoid rounding issues that come up when you convert directly to years).

Then it gets the # of days from their birthday to a week from now, and divides that by 365 to get their age a week from now.

If their birthday is within a week, then the difference between those two values will be 1. So it returns all of those records.