Change all products to taxable goods

[Ajeh]

Assuming the Tax Class Id that you want is 1, you could use:

UPDATE products SET products_tax_class_id = 1 WHERE master_categories_id = XX;

where XX is the master_catgegories_id that you want changed ...

You could set one Product manually then check in phpMyAdmin for this products_id in the table:
products

to confirm the settings that you should use for products_tax_class_id and master_categories_id ...