MySQL join, help needed

[sn202]

Hi all,

I'm pretty new to MySQL and I don't really get the whole join thing, although I understand the theory behind it I have problems when putting it into practice. Basically I'm using PHP with MySQL back end and I've got two tables:

TEST
QUESTION

The primary key of Test is "testno" which is an auto_increment and question has "testno" as a foreign key, so I need a join that will insert the value of "testno" into question when ever a record is entered into TEST based on the "testname" which the user enters into a form.

Let me try and clarify:

$testname = $_POST['testname'];
sql="INSERT into question test.testno where testname = '$testname'";

Obviously this will not work but what I need in effect is a query which carries out this function.

Any help will be much appreciated.

Simon.