Search Box Problems in Dreamweaver

HI

I am having a really stupid problem with my search box.  I have created a form which has a drop down list for 'Positions' and one for 'Location' and then I have a keyword search field.  The keyword search field works fine but I am struggling with the drop down fields.  Currently, if i do not make a selection from both drop down fields and say only make a selection on one, it doesn't bring up any results.  I would like to insert some sort of AND/OR statement in my SQL but not sure how to do this - does anyone have any ideas - this is my current statement:-

SELECT `Position`, Nursery, Location, Salary, Email, ContactNo, JobDescription, JobID, town, jobs.jobtitle

FROM jobs

WHERE `Position` = colname and jobs.Location = varLocation or jobtitle LIKE %colname2% or Nursery LIKE %colname2% or Position LIKE %colname2% or Location LIKE %colname2% or town LIKE %colname2%

Also, I have another two issues if anyone can help:-

I would like to insert a 'Select All' Category  in the drop down field - can't seem to find anything telling me how to do this.  I just want people to be able to select all items in the list if they want to.

Finally, in my drop down lists - when i go into List Values - I have all the positions listed under the label side and exactly the same position listed on the right hand 'Value' side.  All tutorials i read seem to say that you can list values as anything but if i change it to anything other than what is listed as the label it returns a blank result when i carry out the search.  Also, when i changed the label from Nursery Managers to Nursery Managers Jobs it returned a blank result.  I know there is something simple i should be doing/adding somewhere but can't find anything to tell me what. 

Any help would be very much appreciated

THANKS