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Posted by Erland Sommarskog on 03/13/06 10:46
David Portas (REMOVE_BEFORE_REPLYING_dportas@acm.org) writes:
> So couldn't the (simplified) table look like this:
>
> CREATE TABLE hits (hit_datetime DATETIME ip_address VARCHAR(15),
> num_of_hits INTEGER NOT NULL, PRIMARY KEY (hit_datetime, ip_address));
While unlikely, it cannot be excluded that you have two hits from the
same IP-address within 3 ms.
This is a typical case where you need something like IDENTITY. Using
a datetime value is just a gamble. Using a surrogate key which is
assigned for each row is safe.
--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se
Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx
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