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Old December 5th, 2007, 02:53 PM posted to microsoft.public.access.tablesdbdesign
Jamie Collins
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Posts: 1,705
Default Data Primary key vs. Artificial (Autonumber) primary key

On Dec 4, 10:53 pm, Dennis wrote:
ANY data can be used as a Primary Key AS LONG AS you are 100% sure of no
duplication and/or have code in place to prevent such an occurrance.


IIRC a column of type OLEOBJECT cannot be PRIMARY KEY.

Perhaps you meant to say "as long as the engine can be 100% sure of no
duplication"? While I can be sure that I am putting unique values into
a MEMO column, the engine only considers the first 255 characters when
checking a PRIMARY KEY constraint. Also I'd be vary wary of
approximate numeric types (e.g. REAL and FLOAT).

Jamie.

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