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

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