I am having the hardest time trying to figure out how to join tables if data is not present. The field "draftman" is sometimes known and sometimes NULL. I don't have a problem when a value is present, but how can I join the tables JobInfo and Employees when the draftsman value is NULL?

The line
Code:
inner join Employees as dm on JobInfo.draftsman = dm.empID
is where the JobInfo and Employees tables are joined when draftsman is present.

Below is my code:
Code:
$result= mysql_query ("
SELECT JobInfo.SystemNumber, 
       JobInfo.dwgnumber, 
       JobInfo.quotenumber, 
       JobInfo.ponumber, 
       JobInfo.jobnumber, 
       JobInfo.salesperson, 
       JobInfo.draftsman, 
       sp.empID as salesId, 
       sp.empfirstname as salesfirstname, 
       sp.emplastname as saleslastname,
       dm.empID as draftId, 
       dm.empfirstname as draftfirstname, 
       dm.emplastname as draftlastname,
FROM JobInfo 
INNER JOIN Employees as sp ON JobInfo.salesperson = sp.empID 
inner join Employees as dm on JobInfo.draftsman = dm.empID  
") or die (mysql_error());
Thanks for your help in advance.