> > It's all about what's available left-to-right. MySQL can't - still
AFAIK -
> > use parts of an index that are not sequential when using it
left-to-right.
> > See:
> >
> > http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html
> >
> > And use EXPLAIN a lot.
>
> I think I'm starting to under
On Sun, Sep 28, 2008 at 3:02 PM, Hans Zaunere <[EMAIL PROTECTED]> wrote:
>> > So is the first column of a primary key always also an index? I
>> > thought I read somewhere that the columns are concatenated together to
>> > form one index?
>>
>> I don't think they're actually concatenated. The manu
> > So is the first column of a primary key always also an index? I
> > thought I read somewhere that the columns are concatenated together to
> > form one index?
>
> I don't think they're actually concatenated. The manual says:
>
>A multiple-column index can be _considered_ a sorted array
>
On Sat, Sep 27, 2008 at 08:54:10PM -0400, Michael B Allen wrote:
>
> So is the first column of a primary key always also an index? I
> thought I read somewhere that the columns are concatenated together to
> form one index?
I don't think they're actually concatenated. The manual says:
A mult
On Sat, Sep 27, 2008 at 8:32 PM, Daniel Convissor
<[EMAIL PROTECTED]> wrote:
> Hi John:
>
> On Sun, Sep 07, 2008 at 02:31:48PM -0400, John Campbell wrote:
>>
>> With MySQL the fastest is often:
>> Primary(a,b)
>> index(b)
>
> I agree.
>
>
>> And in sometimes you even want:
>> Primary(a,b)
>> index(
Hi John:
On Sun, Sep 07, 2008 at 02:31:48PM -0400, John Campbell wrote:
>
> With MySQL the fastest is often:
> Primary(a,b)
> index(b)
I agree.
> And in sometimes you even want:
> Primary(a,b)
> index(a)
> index(b)
The second index of "a" would duplicate the index of "a" in the primary
key.
> Can anyone recommend which method I should try first?
Don't create the auto increment pk, as it is unnecessary.
With MySQL the fastest is often:
Primary(a,b)
index(b)
And in sometimes you even want:
Primary(a,b)
index(a)
index(b)
I think mysql treats primary key pairs as a simple concatenat
I need a table that will be used basically as a map between records in
another table and I'm not sure how to create the indexes.
At first I thought I would just do something like:
CREATE TABLE map (
id int(5) unsigned NOT NULL AUTO_INCREMENT,
a int(5) unsigned NOT NULL,
b int(
