Message-ID: <51676326.9040807@internode.on.net>
Date: Fri, 12 Apr 2013 11:28:06 +1000
From: Julian Glass <tempura@internode.on.net>
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To: pgsql-admin@postgresql.org
Subject: Re: Invalid SQL not rejected?
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On 12/04/13 10:17, Craig James wrote:
> Hmmm.... the subselect is invalid, but not rejected.  The outer select
> returns every row in the customer_order_matches table.  This seems
> pretty wrong. This is PG 9.2.1 running on Ubuntu.
>
>
> db=> select count(1) from customer_order_matches where
> customer_order_item_id in (select customer_order_item_id from
> customer_order where customer_order_id = 105862140);
>  count
> -------
>  36180
> (1 row)
>
> db=> select customer_order_item_id from customer_order where
> customer_order_id = 105862140;
> ERROR:  column "customer_order_item_id" does not exist
> LINE 1: select customer_order_item_id from customer_order where cust...
>                ^
>
> Craig
The "customer_order_item_id" in the subselect is referencing the
column and therefore the value of the outer query "customer_order_item_id"
in the query result.
i.e:
SELECT generate_series FROM generate_series(1,100) WHERE generate_series
IN (SELECT generate_series);
Which is always going to be true. (x == x).

You might want to explicitly reference tables (and alias). Such as:

SELECT count(*) FROM customer_order_matches com
    WHERE com.customer_order_item_id IN
        (SELECT co.customer_order_item_id
            FROM customer_order co
            WHERE co.customer_order_id = 105862140);

Although I'm making asumptions with the "customer_order_id".
Jules.


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