[Info-ingres] Doing arithmetic with ANSI dates

[Karl Schendel]

> On Oct 27, 2021, at 3:53 PM, Roy Hann <specially at processed.almost.meat> wrote:
> 
> I'm well used to doing arithmetic with the native Ingres DATE
> (INGRESDATE) type, e.g.:
> 
>   SELECT birthdate + '3 months' FROM...
> 
> If birthdate is an ANSI date (ANSIDATE) the above still works
> perfectly well.
> 
> But I doubt that is idiomatic ISO/ANSI SQL. I've Googled a bit and found
> all kinds of syntax being used. I suspect ...+'3 months' or ...-'49
> days' might not work reliably outside of Ingres.

You'll want an INTERVAL.

SELECT birthdate + INTERVAL '3' MONTH FROM ...

Karl