NYCPHP Meetup

[Daniel Kushner]

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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