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Re: BUG #2503: Query results differ based on record count of unrelated table.

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Russell Francis <rfrancis(at)ev(dot)net>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #2503: Query results differ based on record count of unrelated table.
Date: 2006-06-29 13:56:16
Message-ID: (view raw or whole thread)
Lists: pgsql-bugs
Russell Francis wrote:

> If a SELECT statement contains a table in it's FROM clause which has 0
> records in it, the query will not return any results.  If a record is added
> to the table even though it shouldn't modify the results of query, the query
> will return the expected result.
> The SQL statements below are a trimmed down test case which duplicates this
> issue.  The identical SELECT statements return different results depending
> on the record count of the unrelated table_b.
> SELECT table_a.* FROM table_a, table_b WHERE table_a.ta_col_a > 0;

table_b is certainly not unrelated, as it appears in the FROM clause.
So the query is correct to not show any result, per definition of
cartesian product.

Alvaro Herrera                      
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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