Question

i want to make a select, where the users birthday(date field) is less than 30 days.
what is the best way to to do it? i tried datediff, but i don’t know how to put the year aside.

Thanks

Answer 1

You could just use DATEPART function with dayofyear datepart value.

EDIT: honestly, there is a boundary issue in my previous answer (many thanks to Damien): e.g. 2010-12-25 and 2011-01-07 => the difference should be less then 30 days, but DATEPART(dayofyear, @date) - DATEPART(dayofyear, [Birthday]) < 30 condition would skip this record. So I added an additional contition to my answer:

DATEPART(dy, @d) - DATEPART(dy, [Birthday]) < 30 OR
(
   DATEPART(mm, @d) = 12 AND
   DATEPART(dy, DATEADD(m, 1, @d)) - DATEPART(dy, DATEADD(m, 1, [Birthday])) < 30
)

it adds one month to the each date in the case when the month part of the first date is December and compares the difference.