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Meanwhile, here's an alternative solution to my previous one, this one without the SQL variables. SELECT SUM(CASE WHEN DATE(datein) > DATE(dateout) THEN DATEDIFF(datein, dateout) - 1 ELSE 0 END ) as tot_absent FROM ( SELECT a.dateout , MIN(b.datein) as datein FROM ajoo_login a LEFT JOIN ajoo_login b ON a.dateout < b.datein GROUP BY a.dateout ) logins; +------------+ | tot_absent | +------------+ | 327 | +------------+

OK, I loaded your data into a test table INSERT INTO ajoo_login (datein, dateout) VALUES ('2019-03-30 17:05:24', '2019-03-30 17:09:47'), ('2019-04-01 15:13:32', '2019-04-01 15:19:46'), ('2019-04-04 23:37:21', '2019-04-04 23:50:51'), ('2019-04-18 15:28:35', '2019-04-18 15:33:10'), ('2019-04-23 16:35:20', '2019-04-23 16:42:35'), ('2019-04-24 12:03:07', '2019-04-24 12:10:28'), ('2019-05-01 08:05:48', '2019-05-01 08:20:28'), ('2019-05-08 18:04:04', '2019-05-08 18:14:57'), ('2019-05-09 08:18:15', '2019-05-09 08:29:38'), ('2019-06-18 12:49:01', '2019-06-18 13:10:15'), ('2019-09-05 17:17:33', '20

NOTE: both instances of $db->query(..) in the above post should be $db->prepare(..)

Because of the JOIN, it is initialized before it is used. As an alternative to the join you could have two queries ... SELECT @prevout := NULL; -- initialize @prevout SELECT SUM(diff) AS tot_absent FROM ( SELECT CASE WHEN DATE(datein) > DATE(@prevout) THEN DATEDIFF(datein, @prevout) - 1 ELSE 0 END AS diff , datein , @prevout := dateout AS dateout -- store dateout in @prevout FROM ajoo_login ) logins; @vars are just like va

Where did that suddenly spring from? There's no mention in your original post. Don't keep us in the dark and still expect help.

My version would be to JOIN the table to itself once or twice in order to pair up consecutive records, then DATEDIFF()-1 the end of the first with the start of the second, then SUM the results.

Well, this would be one of those times. You can't do simple math like $now - $last with the value returned by microtime(). You need to use microtime(true) for that. For example: <?php $last = microtime(); sleep(5); $now = microtime(); $diff = $now - $last; printf("%0.4f seconds have passed", $diff); One might expect since the script sleeps for 5 seconds to get a result like 5.xxxx seconds have passed but what you actually get is: Notice: A non well formed numeric value encountered in W:\expired.php on line 7 Call Stack: 0.0002 391984 1. {main}() W:\expired.ph

plogsID=plogsID will always be true. SELECT * FROM blogs WHERE blogsStatus=1 AND blogsID=blogsID You have several options. See https://www.php.net/manual/en/pdo.prepare.php, but to get you started... $stmt = $db->query('SELECT * FROM blogs WHERE blogsStatus=1 AND blogsID=:blogsID'); $stmt->execute(['blogsID' => $blogsID]); $result = $stmt->fetch(PDO::FETCH_ASSOC); $stmt = $db->query('SELECT * FROM blogs WHERE blogsStatus=1 AND blogsID=?'); $stmt->execute([$blogsID]); $result = $stmt->fetch(PDO::FETCH_ASSOC); Or you can use use bindParam() or bindVal

You were close with your original method but it needed a couple of tweaks while fetch { if $type != $t { if $t != '' output </optgroup> // only close previous group if there was one output <optgroup> $t = $type end if output <option> end while output </optgroup> // close final group

I have an inflateable baseball bat which I often use on such occasions.

What if you echo the query string to examine the syntax? echo "SELECT * FROM MK_migration_details WHERE mig_bid='".$_SESSION['bid']."'";

Telling us what the problem is goes a long way towards getting it resolved.