Re: Assigning a timestamp without timezone to a timestamp

Hi Tom,

Thanks again, I did not appreciate the dual function of "AT TIME ZONE" when
the input is timestamptz then the function converts from one timezone to
another (not what I wanted),

but when the input is timestamp the function acts more like a cast than a
convert (exactly what I wanted)

I must disagree with your assertion about the redundancy of:
> , cast(start_datetime as timestamp(0) without time zone)::timestamp at
> time zone B.timezone_ch

what I am doing is taking a timestamptz, discarding its timezone, and then
casting it to another timezone

for example from 2006-10-03 09:00:00 NZST to 2006-10-03 09:00:00 EST5EDT

If I am missing a much easier way to accomplish this please let me know.

Tom Lane-2 wrote:
>
> chrisj <chrisj(dot)wood(at)sympatico(dot)ca> writes:
>> When I first saw your solution I thought it was logically going to do
>> (notice the parentheses):
>> select ('2006-07-13 09:20:00'::timestamp) at time zone 'EST5EDT';
>> which does not help
>
> Well, actually, that's exactly what it does. AT TIME ZONE is an
> operator that converts timestamp without time zone to timestamp with
> time zone (or vice versa). I guess you could easily get confused
> here, but AT is not WITH.
>
>> , cast(start_datetime as timestamp(0) without time zone)::timestamp at
>> time zone B.timezone_ch
>
> That's redundant --- you're casting the result of the cast to timestamp
> (implicitly without time zone), then applying the AT TIME ZONE operator.
>
> regards, tom lane
>
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