Question

I have activity logs stored in my mysql database, each with a registered datetime. I am trying to write a short php script to delete all logs that are older than 60 days. I am having trouble trying to compare the times in datetime format.

Here’s what I have:

$sixty_days_past = strtotime("-60 days");

$earliest_time = date("Y-m-d H:i:s", $sixty_days_past);

$logs_result = mysql_query("SELECT id FROM df_logs WHERE date < '$earliest_time'");

    while($logs_row = mysql_fetch_array($logs_result)) { 

        $oldentry = $logs_row['id'];

        mysql_query("DELETE FROM df_logs WHERE id='$oldentry'");    

    }

What is wrong with this query?

Answer 1

Everything.

DELETE FROM `df_logs` WHERE `date` < DATE_ADD(NOW(),INTERVAL -60 DAY)

Done.

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To elaborate:

• You are going through PHP when MySQL is perfectly capable of doing the right calculations
• You are not enclosing field names in backticks, which is a problem because date is a keyword.
• You are deleting rows one at a time, which results in a potentially unbound number of queries, instead of deleting them all at once (such as with IN to list the IDs to delete)