NYCPHP Meetup

[Peter Lehrer]

found it. thanks.

peter

On Sun, 15 Jun 2003, Daniel Kushner wrote:

> Peter,
>
> You can set mutilple fields in a table to be a primary key. In general, the
> combination of the field makes the key.
> http://www.mysql.com/documentation/mysql/bychapter/manual_Reference.html#CRE
> ATE_TABLE
>
> Look at the line:
> PRIMARY KEY (index_col_name,...)
>
> --Daniel
>
> > -----Original Message-----
> > From: Peter Lehrer [mailto:pl at eskimo.com]
> > Sent: Sunday, June 15, 2003 12:12 AM
> > To: NYPHP Talk
> > Subject: Re: [nycphp-talk] primary keys
> >
> >
> > I see.
> > I think I confused a primary key using a combination of columns in a table
> > versus having 2 primary keys in a table, which obviously can't exits.
> > Thanks for your help.
> >
> > Peter
> >
> > ----- Original Message -----
> > From: "David Mintz" <dmintz at panix.com>
> > To: "NYPHP Talk" <talk at nyphp.org>
> > Sent: Saturday, June 14, 2003 11:40 PM
> > Subject: Re: [nycphp-talk] primary keys
> >
> >
> > > On Sat, 14 Jun 2003, Peter Lehrer wrote:
> > >
> > > > Is it possible to have two primary keys in one table, such as primary
> > key 1
> > > > and primary key 2, or is that a contradiction in terms? Would second
> > primary
> > > > key have to be a "unique"?
> > >
> > > You can only have one primary key. If you're thinking about a
> > unique index
> > > on multiple columns, yes you can do that, and indeed there are
> > situations
> > > where you do. You might not need any primary key in that case.
> > >
> > > I'll give you an example. I have a table called 'interpreter' (of
> > > languages) and a table called 'language'. Some interpreters
> > have multiple
> > > working languages; lots of languages are spoken by more than one
> > > interpreter. You resolve the many-to-many relationship with a
> > third table
> > > called interpreter_language which looks something like this (English is
> > > asumed in this particular application, so I only one the 'foreign'
> > > language to store each interpreters' language pair). Note the
> > unique key:
> > >
> > > CREATE TABLE interpreter_language (
> > >   interpreter_id smallint(5) unsigned NOT NULL default '0',
> > >   language_id smallint(5) unsigned NOT NULL default '0',
> > >   UNIQUE KEY idx1 (interp_id,lang_id)
> > > ) TYPE=MyISAM;
> > >
> > > Insertion fails if somebody tries to enter a duplicate record.
> > >
> > > HTH!
> > >
> > >
> > > ---
> > > David Mintz
> > > http://davidmintz.org/
> > >
> > >      "You want me to pour the beer, Frank?"
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
> >
>
>
>
>
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