Inserting Image Name into the database

I have created a form with a file field to upload an image and insert its name directly into the mysql database. The column type is varchar where the name will be inserted through the form. Now i am getting two problems. All the fields get filled out in the database except the image name. The image name must be inserted into the productImage column. It remanins null. No image is uploaded to the destination folder.

And also on submitting the form, I get this error.
Error Executing Database Query.
Column 'productID' cannot be null

I am attaching the full code. Could someone help out? All i require is that the file is uploaded and name inserted into mysql database in specified column.