Calculate age with decimals from date of birth - mysql

Question

I have a dob field in my MySQL table that's of type date. Just a small, trivial example is something like this:
mysql> select dob from players limit 5;
+------------+
| dob |
+------------+
| 1983-12-02 |
| 1979-01-01 |
| 1989-05-11 |
| 1976-03-24 |
| 1989-09-12 |
+------------+
I am trying to calculate ages with decimal points by using today's date. So technically if your birthday is June 1, 1981 or 1981-06-01, that makes you 33 and today is June 7.. you'd be 33.(6/365) or 33.02 years old. What's the easiest way to calculate this using SQL?

Answer 1

Usually DOB calculation is pretty easy in mysql when you want to calculate the years without any fraction something as
mysql> select timestampdiff(YEAR,'1981-06-01',now());
+----------------------------------------+
| timestampdiff(YEAR,'1981-06-01',now()) |
+----------------------------------------+
| 33 |
+----------------------------------------+
But since you need the fraction also then this should do the trick
mysql> select format(datediff(curdate(),'1981-06-01') / 365.25,2);
+-----------------------------------------------------+
| format(datediff(curdate(),'1981-06-01') / 365.25,2) |
+-----------------------------------------------------+
| 33.02 |
+-----------------------------------------------------+
Year is considered as 365.25 days.
So in your case you may have the query as
select
format(datediff(curdate(),dob) / 365.25,2) as dob
from players limit 5;

Answer 2

You can use the to_days function to calculate the days between the year zero and someone's birthday. Then subtract from today that number of days. That should give you the birthday as if someone was born in the year zero:
select year(subdate(now(), to_days(dob)))
Example at SQL Fiddle.

Answer 3

There are a couple of issues. you are using 365 as the number of days in a year and ignoring leap years.
The easiest way to do this would be
select datediff( now(), '1981-06-01' )/365.25;
When you use 365.25 it will spread the leap year and you should be fine. MySQL says this value is 33.0157. when you round it off to two decimals you should be fine.

Answer 4

Your best bet is use of DATEDIFF() as follows:
select datediff(NOW(),date("1983-12-02"))/365;
where the quoted date is your date field, so your example would translate to:
select datediff(NOW(),date(dob))/365 from players limit 5;
The result is returned would be the number of years since the birth date to 4 decimal places.
If you prefer two decimal places use truncate() as follows:
truncate(datediff(NOW(),date("1983-12-02"))/365,2);