List:General Discussion« Previous MessageNext Message »
From:Paul DuBois Date:April 6 2002 1:35pm
Subject:Re: Difference between Unique Index and Primary Key?
View as plain text  
At 1:24 -0600 4/6/02, BD wrote:
>Paul,
>         Do you know if there is any performance differences between 
>a unique index and primary key (if there are no nulls)?
>         Is the index file format the same as the primary key?

I cannot answer that with absolute certainty, but as far as I know the
answers are no, and yes.

>
>Brent
>
>At 05:09 PM 4/5/2002, you wrote:
>>>Here are a few easy philosophical questions for a change:
>>>
>>>1) For performance or storage benefits, is there a difference between a
>>>Unique Index and Primary Key?
>>
>>There can be only one primary key.  There can be multiple unique indexes.
>>
>>Primary keys cannot contain NULL values.  Unique indexes can allow NULL
>>values (and in fact, NULL is the one value that can occur multiple
>>times in a unique index).
>>
>>>
>>>2) Is there a reason why I should use Primary Key instead of a Unique Index?
>>>
>>>3) Why isn't there a syntax for "create primary index index_name on
>>>table_name (fieldlist)" ? I know a primary key can be added with "Alter
>>>table", but if I'm defining indexes for a table, it would look a lot better
>>>in the script if I was using the same syntax.
>>>
>>>TIA
>>>
>>>Brent
>>>
>>>sql, query

Thread
Difference between Unique Index and Primary Key?BD6 Apr
  • Re: Difference between Unique Index and Primary Key?Paul DuBois6 Apr
    • Re: Difference between Unique Index and Primary Key?BD6 Apr
      • Re: Difference between Unique Index and Primary Key?Paul DuBois6 Apr