如何更新临时数据库中的列

I need to update a column from a temporary database created in mySQL. I've tried to change the variable but it's not work. Here's my script:

$sid=md5(time());//new value
mysqli_query($con,"CREATE TEMPORARY TABLE tmptable_2 SELECT * FROM prop_itinerary WHERE prop_sid = '$_GET[sid]'");
mysqli_query($con,"UPDATE tmptable_2 SET prop_sid ='$sid'");//this is where I need to change the prop_sid from the original 'prop_itineraty.prop_sid'
mysqli_query($con,"INSERT INTO prop_itinerary SELECT * FROM tmptable_2");
mysqli_query($con,"DROP TEMPORARY TABLE IF EXISTS tmptable_2");

When I print out UPDATE tmptable_2 SET prop_sid ='$sid' it turns out the $sid correctly. But still when it inserted into DB it is a sid from prop_itinerary.prop_sid.