Do you have two identical tables? If not, then doing a select the way you
propose won't yield any rows. If they are identical, then you've already got
the data, and so wouldn't need to select anything. I'm sure I'm
misunderstanding exactly what you're trying to do, so maybe you could
explain it a bit further.
In any case, if you've got a unique key that tied the two tables together
(or if you could set it up so that you did), that would be your best bet.
Using all those values in your where clause is going to slow your selects
down considerably if there aren't keys on them (and if the number of columns
is variable, it would probably be difficult to have the keys to handle all
combinations of columns).
Brian McCain
----- Original Message -----
From: "Hal Vaughan" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, March 21, 2003 2:29 PM
Subject: Selecting identical rows from 2 tables (basically Row AND Row)
I posted earlier this week about how to select from two different tables
with
an OR -- selecting rows from either table and putting them into one.
That was easily accomplished with a UNION statement (AFTER upgrading to
MySQL 4.0.x).
Now I'm doing almost the opposite. I have two tables, TestCases, and
TestTemp
(a temporary table). I want to select any rows in TestCases AND TestTemp.
I
know I can do that if I go through and match field by field:
SELECT * FROM TestCases AS C, TestTemp AS T WHERE
C.Field1 = T.Field1 AND C.Field2 = T.Field2;
(and so on if there are more fields).
Is there a shortcut to this? Is there a quick way to say
SELECT * FROM TestCases AS C, TestTemp AS T WHERE (allfields = allfields);
I'm calling from Perl, so I can write a routine that will go through and
list
every darn field, but I'd like to find a shorter and faster way to do it.
Thanks!
Hal
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