Designing a database structure for huge sets of form data I am converting a form that takes up 35 pages of A4 size to a web based version, and will need to retain the data for each form submission in a MySQL database.

The form is complex and we could be looking at over 500 individual fields for each form submission.

I've been reading about the EAV data approach, which seems like it might be a good option. The info I was reading for EAV however suggested it was only a good choice for sparse matrix data, which I imagine this will not be. 

500 columns seems like bad design, what do you think?
Have 'real' columns for a few of the fields -- the ones that you are likely to search or filter on.  Throw the rest (or, simply, all) of the fields into a big JSON string as another column.  Perhaps MEDIUMTEXT.