Saving queries and optimizing a database

I'm creating a script that is designed to query a list of posts by selecting a category, sub category and another sub, or by selecting all.

The problem is that when I want to show 'all' posts I need to create 3 queries for each post (to convert the category number into name).

Is there a way to make it more optimized?

Tables structure:

posts:

• id (int)
• main_cat (main category) (int)
• sub_cat (sub category) (int)
• sub_sub_cat (sub to the sub) (int)
• description (varchar)

main_cat:

• id (int)
• name (varchar)

sub_cat:

• id (int)
• relation (int) (id of the main_cat)
• name (varchar)

sub_sub_cat:

• id (int)
• relation (int) (id of the sub_cat)
• name (varchar)

Thanks in advance.