Re: Calculation error

chestie <mcit(at)argus(dot)net(dot)au> writes:
> I kept getting this same error, heres what I was trying to do.

> it := select int4(extract(epoch from timestamp $1 -
> extract(epoch from timestamp $2));

You should just write

it := select int4(extract(epoch from $1) -
extract(epoch from $2));

You are confusing the syntax
timestamp 'string literal'
(or more generally, any type name followed by a string literal) with
something that you should apply to a non-constant value. That syntax
works *only* for literal constants.

In your example, $1 and $2 are already of type timestamp and require
no further conversion, so the extract()s will work fine as I show above.
If you did need a run-time type conversion, you'd have to write
"CAST($1 AS timestamp)" (the SQL-spec-approved syntax) or
"$1::timestamp" (Postgres' traditional notation).

regards, tom lane