Sure I am not sure it is a good ide to have s_category_id is field table were you put all category belonging to the field. this is forcing to do long scan to the field. can we have a table category field to link both of them instead of having this huge text field

Why it should be huge?

if you have a lot of categories. i you need to associated them to attribute

Index that column.
I do not consider varchar 1000 huge, as osclass description might be easily 20000 of characters...

Thank you