Database Tables

wp_commentmeta
- meta_id
- comment_id
- meta_key
- meta_value
wp_comments
wp_links
wp_options
wp_postmeta
- Used for both posts AND pages. This is where custom fields attached to a post/page would store their data.
- $wpdb->postmeta
- meta_id
- post_id
- meta_key
- meta_value
wp_posts
- All content types are kept in the wp_posts table and are distinguished from one another by a post type. Default post types are post, page, attachment, revision, and navigation menu.
- Navigation Menu – nav_menu_item – This is not an entire menu but a single navigational item on a larger menu.
wp_terms
- For the taxonomy system, contains categories, tags, and custom taxonomies.
wp_term_relationships
- When terms are hierarchical the relationship between one term and another is stored here. This table is being merged into wp_terms in the future.
wp_term_taxonomy
- Used to determine which terms are actually the root level of a taxonomy.
wp_usermeta
wp_users

Methods for Saving Data to Database

Option Mechanism – For small amounts of data that rarely changes.
- Best practice is to use as few as possible, consider including multiple values in a single option field.
- add_option($name, $value, $deprecated, $autoload);
  - Only creates if it doesn’t already exist
  - $(option_)name = name of option; $value = default value (optional); $deprecated = no longer used, pass an empty string or null to it if you want to use $autoload; $autoload = should option be loaded by wp_load_alloptions function? by default is yes.
- getoption($option);
  - Retrieve the option from DB.
- update_option($option_name, $newvalue);
  - Can be used to create an option if the deprecated or autoload params are not needed.