Question

basically, I have a cookie with the category slug stored, using this data I want to query the database and return the ID of the category.

I am new to mysql and this seems like an advanced query that may need to use joins, any help or guidance would be much appreciated.

Thank you!

Reference:
http://codex.wordpress.org/File:WP3.0-ERD.png

Answer 1

SELECT wp_term_taxonomy.term_taxonomy_id
FROM   wp_terms
  JOIN wp_term_taxonomy USING (term_id)
WHERE  wp_term_taxonomy.taxonomy = 'category'
   AND wp_terms.slug = ?

Learn about SQL joins.