<snip>
>>
>> SELECT COUNT(*) AS num FROM alerts WHERE stamp > DATE_SUB(NOW(),
>> interval 300 second) AND devid=244;
>>
>> With this query, MySQL will run DATE_SUB() once, and then use the
>> index on stamp (which I assume you have) to narrow down the result set.
>>
[JS] I don't understand how an index on a timestamp would help. Theoretically,
each record could have a unique value for the timestamp; so the index would
have an entry for each record. Would MySQL really use that in preference to,
or in combination with, an index on devid?
Regards,
Jerry Schwartz
Global Information Incorporated
195 Farmington Ave.
Farmington, CT 06032
860.674.8796 / FAX: 860.674.8341
E-mail: jerry@stripped
Web site: www.the-infoshop.com
>> Steve
>>
>That did it! Thank you.
>
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