Re: Why is this a cross join?

On 2/17/2013 2:09 PM, Tim Uckun wrote:
> Say I created new columns on both tables called "first_6" and
> populated them with the substrings.  If I did a inner join or a left
> join on those fields would I still get a cross join?
>
> inner join model_configurations mc on mc.first_6 = crm.first_6

without additional filtering, that will return a row for every row in
crm that matches a row in mc.    if there's a 1000 rows in crm that each
match an average of 6 rows in mc, that would return 6000 rows.

crm left join mc would return all of those, plus all the rows in crm
that don't have any match in mc (the mc.* fields would be NULL in these
result rows).



--
john r pierce                                      37N 122W
somewhere on the middle of the left coast