MySQL Error#: 1054 Unknown column 'colname3' in 'on clause'

I am trying to use the following query thats filtered from a URL Variable

SELECT children.childrenEmailAddress
FROM children JOIN activities ON activities.activitySection = children.childrenSection AND activityID = colname3
LEFT JOIN signupActivity ON signupActivity.signupActivitychildID = children.childrenID
WHERE signupActivity.signupActivitychildID IS NULL

However I get an error about using colname3 within an ON statement

MySQL Error#: 1054
Unknown column 'colname3' in 'on clause'

Do you know how I can resolve this please?

Did you define colname3 as a parameter? It looks like it didn't get defined properly in the Recordset to come from the url variable.

Hi Ray

Dreamweaver added the code for me and it seemed as I would expect.

For now I have worked around by replacing colname3 with '".$_GET["activity"]."'

That will leave a SQL injection hole in your code and make it hackable. You should add that as a URL parameter in your recordset.

All sorted now.

I rebuilt the page from scratch and it worked ok this time.