> All I need is a list on the Usernames that are in one column but not the
> other.

SELECT table1.Username
FROM table1 left join table2 on (table1.Username = table2.Username)
WHERE table2.Username is NULL;

Mikhail.

----- Original Message -----
From: "Simon Green" <[EMAIL PROTECTED]>
To: "Mysql (E-mail)" <[EMAIL PROTECTED]>
Sent: Thursday, June 27, 2002 10:01 AM
Subject: Cartesian Product


> Sorry I should have made this a bit clear.
> I have to tables with users names in them.
> All I need is a list on the Usernames that are in one column but not the
> other.
> The problem is like Mr DuBois said, is that I get every possible match
like
> a matrix (I think?).
> So how do I get the values that are just not it one column?
>
> Thanks
> Simon
>
> -----Original Message-----
> From: Paul DuBois [mailto:[EMAIL PROTECTED]]
> Sent: 27 June 2002 05:00
> To: Simon Green; Mysql (E-mail)
> Subject: Re: Cartesian Product
>
>
> At 13:22 +0100 6/26/02, Simon Green wrote:
> >Hi
> >When I run my MySQL question I get what I think is a cartesian product?
> >
> >SELECT table1,Username
> >FROM table1, table2
> >WHERE table1.Username != table2.Username;
> >
> >If I just run'=' then no problem but it seems to what to match every
thing
> >with every thing
> >and so I run out of memory.
> >Is there a way to do a distinct match?
> >Thanks
> >Simon
>
> What do you mean by "distinct match"?
>
> Your != query is effectively a cartesian product that retrieves all but
the
> diagonal elements of the matrix.
>
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