如何从数据库中删除过期数据（取决于句点列）

Question

I want to delete the data that expired.

I have two columns:
created_time : That contain a value indicate to time() function (ex: 1395836716).
period :That contain the period of the remain the row in database (ex: 3 or 7 or 15 or 30 per day).

I want to create a query to check on all rows in the table to know the rows that expired.
The problem is I don't know how to do that, but I tried.

$twentyFour = 60 * 60 * 24;
mysql_query("DELETE FROM content WHERE created_time + (period * $twentyFour ) > '" . time() . "' ");

But unfortunately, did not work as I expected.

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Edit:

This is a result of row

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Edit 2

I did it, by using php conditions:

$twentyFour = 60 * 60 * 24;
$query = mysql_query("SELECT * FROM content");
while ($data = mysql_fetch_assoc($query)) {
    if ($data['created_time'] + ($data['period'] * $twentyFour) < time()) {
        mysql_query("DELETE FROM content WHERE id = $data[id]");
    }
}

The previous code works fine as was I want.
the problem is the previous code will occurs more server load.
I want a query to doing as the previous code does without using conditions.

Answer 1

May I suggest you edit your data structure and include a new column delete_time?

This delete_time should contain the UNIX timestamp of when your column should be deleted calculated from your given period.

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Assuming your POST data of the period is numerical value indicating the number of days to save the data for, delete_time should be calculated by

$delete_time = time() + $_POST['period']*24*60*60;

This way, your pruning/deleting query can just be a one-liner:

mysql_query("DELETE FROM content WHERE delete_time < ".time());

That query deletes all rows whose delete_time has passed the current time().