plot.php mysql

[chandra50]

In plot.php I get the following error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '!, FROM raw_logs WHERE sessi' at line 1

// Get data for session
$sessionqry = mysql_query("SELECT time,$v1,$v2
                      FROM $db_table
                      WHERE session=$session_id
                      ORDER BY time DESC;") or die(mysql_error());

mysql version (in Ubuntu 14.04) is
mysql Ver 14.14 Distrib 5.5.47, for debian-linux-gnu (x86_64) using readline 6.3

Looks like this issue has been discussed earlier.
Could you please let me know the resolution.
Thanks.