CSV Import of a product in two or more categories

Wich could be the sintax of importing a product via csv import and have it listed on two diferent categories?
By the way, when i used csv import for the first time i realized that in the categories and parent_category colums i got only the names of that categories and not the category ID number.

Then reading a post in the forum i see that is possible to use the category ID instead of the name (wich really create a mess when importing into categories with "commas" on the title), do i have to change all the category names in my csv to the ID number of that category for better integration and avoid problems with commas in the title of the description?

If i change the value of the column "categories" in my existing csv's will them update my products as usual?

My csv actually have these rows only:

product_code;product_parent_id;product_name;product_description;product_tax_id;product_type;categories;price_value;price_currency_id;price_min_quantity;price_access;images;