How to execute datediff on multiple rows

Question

I want to do something like this:

select datediff('2010-01-21',(select date_of_birth from people));

and take as result the difference from each date_of_birth.

Answer 1

You can use datediff to get Difference in terms of day or specified format (either month, week year, days etc)

select datediff(DAY,'2010-01-21',date_of_birth)
from people