Re: date interval

At 07:12 PM 5/4/05, Frank Bax wrote:
>At 04:44 PM 5/4/05, Keith Worthington wrote:
>>I need to generate a column representing the interval passed in months and
>>restrict the returned data to those intervals matching 12, 24, 36 and 48.
>>
>>So far by reading the documentation I have gotten to these
>>expressions. But I
>>do not know how to get the number of months out of this.
>>
>> current_date - tbl_detail.ship_by_date AS elapsed_x
>> age(tbl_detail.ship_by_date) AS elapsed_y
>>
>>Once I get that I am thinking that I can use the same expression with the IN
>>to get the desired results.
>
>
>date_part('epoch', age(tbl_detail.ship_by_date)) / (60*60) AS elapsed_y
>
>instead of "IN (12,24,36,48)" you might also consider something like
> where elapsed_y between 12 and 48 and elapsed_y %12 = 0
>
>You'd have to run your own tests to see which is faster. An index might help:
> date_part('epoch', age(tbl_detail.ship_by_date)) / (60*60)
>or maybe (not sure if this one would get used):
> ( date_part('epoch', age(tbl_detail.ship_by_date)) / (60*60) ) % 12

Ooops, I thought you said hours - for months, something like this might work...

( date_part('year', xx) * 12 + date_part('month', xx) )