Re: select based on multi-column primary keys

No...  its a table constraint using a unique, implicit index on the listed 
columns. .

PRIMARY KEY ( column [, ...] )

The PRIMARY KEY table constraint is similar to the PRIMARY KEY column 
constraint. As a table constraint, PRIMARY KEY allows multiple columns to be 
defined in a parenthetical expression, separated by commas. An implicit 
index will be created across columns. The combination of values for each 
column specified must therefore amount to only unique and non-NULL values, 
as with the PRIMARY KEY column constraint.



hehehe....


"Andrew Sullivan" <ajs@crankycanuck.ca> wrote in message 
news:20070121152838.GB3533@phlogiston.dyndns.org...
> On Fri, Jan 19, 2007 at 07:45:40PM -0800, codeWarrior wrote:
>> AFAIK: You cannot have multiple primary keys. How would you know which 
>> one
>> is the actual key ?
>
> You can have a multi-column primary key, though.  That's a perfectly
> legitimate approach.
>
>> FYI: What you are really talking about are table contraints... When you 
>> have
>
> No, it's a multi-column primary key.
>
>> My advice would be to alter your table structure so that you have a 
>> "real"
>> PK not table constraints -- that would make it searchable....
>
> This is already searchable.  What you are talking about is not a real
> primary key, but an artificial one.  The OP already has a real
> primary key.  SQL purists think artificial primary keys mean that you
> haven't done enough normalisation.  I'm going to remain silent on
> that topic, though, so that we don't get a Thread That Does Not End
> :)
>
> A
>
>
> -- 
> Andrew Sullivan  | ajs@crankycanuck.ca
> If they don't do anything, we don't need their acronym.
> --Josh Hamilton, on the US FEMA
>
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