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Date: Tue, 21 Mar 2006 17:03:02 -0800 (PST)
From: Stephan Szabo <sszabo@megazone.bigpanda.com>
To: "Davidson, Robert" <robdavid@amazon.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Using a parameter in Interval
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On Tue, 21 Mar 2006, Davidson, Robert wrote:

> No matter how I try to concatenate, I can't seem to get a parameter to be used by INTERVAL in a function:
>
> CREATE OR REPLACE FUNCTION Testing(TrailingWeeks int) RETURNS date AS $$
> BEGIN
> 	RETURN current_date - INTERVAL (CAST(TrailingWeeks AS varchar) || ' weeks');
> END;
> $$ LANGUAGE plpgsql;
>
> --select * from testing(1);
>
> ERROR:  syntax error at or near "CAST" at character 34
> QUERY:  SELECT  current_date - INTERVAL (CAST( $1  AS varchar) || ' weeks')
> CONTEXT:  SQL statement in PL/PgSQL function "testing" near line 2
>
> I have tried concatenating it as a declared variable (with and without apostrophes)
> 1 weeks
> And
> '1 weeks'
>
> With no success. Any tips?

You'd need a cast, not INTERVAL foo as the latter is for interval literals
(and CAST... is not a valid interval literal even if the output of the
concatenation looks like an interval literal).  I'd go with the suggestion
of using int * interval instead of concatenation in any case.