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From: David G Johnston <david.g.johnston@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Re: Parameterized Query
Date: Mon, 9 Jun 2014 06:36:13 -0700 (PDT)
Message-ID: <1402320973871-5806502.post@n5.nabble.com> (raw)
In-Reply-To: <1402300317130-5806470.post@n5.nabble.com>
References: <1402300317130-5806470.post@n5.nabble.com>
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frankliu747 wrote
> I have a query that works on sql sql server or oracle  that do a
> parameterized query, I would like to move this to postgreSQL but I'm just
> not sure how to get it done. This is the query 
> select * from quest q 
>    left join ask a on q.ask_id=a.id 
> where q.createtime>=:StartDate and q.createtime<=:EndDate
>         and a.asktime>=:StartDate and asktime<=:EndDate
> 
> i need to  define parameters in the WHERE clause to build dynamic
> SELECT,like ":StartDate" may be repeat more than one time.
> 
> This works great on SQL Server or oracle  but not on postgreSQL. Any help
> would be appreciated. 
> 
> and i use sql server reporting service use odbc connect postgres 9.34

The main SQL executor does not support named parameters, though psql does
since it has its own pre-parse step before sending the query to the server.

The typical way of doing this in PostgreSQL is to create a table returning
function with as many arguments as you have parameters.  Within the function
body you can reference the input arguments repeatedly.

CREATE FUNCTION do_query(startdate date, enddate date)
RETURNS TABLE (col1 text,col2 date)
AS $func$

SELECT col1, col2 FROM tbl WHERE (col2 BETWEEN startdate AND enddate) AND
(col3 BETWEEN startdate AND enddate);

$func$
LANGUAGE SQL
;

Note that you do not use any special prefix to refer to the arguments in the
query.

In the client you call the function, with, parameters, using the following
query:

SELECT col1,col2 FROM do_query(?,?);

The documentation on CREATE FUNCTION as well as both the SQL and pl/pgsql
languages will be of great assistance on this topic.

David J.




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