Re: why does this select hang postgres???

On Fri, 10 Aug 2001, Mike Mascari wrote:

> Jeremy Hansen wrote:
> >
> > select * from env_info,summary,plat_info;
> >
> > Is my statement broken? Is this not legal? Postgres just sits there....
>
> Its quite possibly broken. It's legal to PostgreSQL; other databases
> won't like the missing FROM clause. But PostgreSQL will generate the
> Cartesian product of all three tables. If table 1 has 100 rows,
> table 2 has 100 rows, and table 3 has 100 rows, PostgreSQL will have
> to construct and return 100 * 100 * 100 rows = 1,000,000 rows.
> >
> > My goal is to select everything from multiple tables with one sql
> > statement.
>
> Are you sure you want each row of each table combined with each row
> of each of the other tables? If these tables are related in any way
> you have to provide a WHERE clause that specifies the relationship.

Ok, I limited this using a where clause and it's still killing postgres:

select * from summary,env_info,plat_info where summary.bug_id=81;

thanks
-jeremy

> >
> > Thank You!
> > -jeremy
>
> Mike Mascari
> mascarm(at)mascari(dot)com
>

--
salad.