WordPress Multisite adds network-level tables and per-site table copies.

Network Tables

These tables exist once per network, typically without a numeric prefix.

wp_blogs

Stores all sites in the network.

Indexes:

• PRIMARY (blog_id)
• domain (domain(50), path(5))
• lang_id (lang_id)

wp_site

Stores network definitions (for multi-network setups).

Indexes:

• PRIMARY (id)
• domain (domain(140), path(51))

wp_sitemeta

Network-wide options (like wp_options but for the network).

Indexes:

• PRIMARY (meta_id)
• meta_key (meta_key(191))
• site_id (site_id)

Common sitemeta keys:

• site_name – Network name
• admin_email – Super admin email
• active_sitewide_plugins – Network-activated plugins
• site_admins – Super admin usernames
• registration – Registration settings
• blog_upload_space – Upload quota per site

wp_blogmeta

Per-site metadata (added WordPress 5.1).

Indexes:

• PRIMARY (meta_id)
• meta_key (meta_key(191))
• blog_id (blog_id)

wp_registration_log

User registration log (legacy).

wp_signups

Pending user/site signups awaiting activation.

Per-Site Tables

Each site in a multisite network gets its own set of core tables with a numeric prefix:

Shared Tables

These tables are shared across all sites:

• wp_users – Single user table for entire network
• wp_usermeta – User meta with per-site capabilities

Per-site user capabilities:

wp_capabilities     → Main site roles
wp_2_capabilities   → Site 2 roles
wp_3_capabilities   → Site 3 roles

Common Queries

List all sites

SELECT blog_id, domain, path, registered 
FROM wp_blogs 
WHERE deleted = 0 AND spam = 0 
ORDER BY blog_id;

Get site by domain

SELECT * FROM wp_blogs 
WHERE domain = 'example.com' 
  AND path = '/';

Get network options

SELECT meta_key, meta_value 
FROM wp_sitemeta 
WHERE site_id = 1;

Get super admins

SELECT meta_value 
FROM wp_sitemeta 
WHERE meta_key = 'site_admins';

Count posts across all sites

SELECT 
  b.blog_id,
  b.domain,
  (SELECT COUNT(*) FROM CONCAT('wp_', IF(b.blog_id=1,'','2_'), 'posts') 
   WHERE post_status='publish') as post_count
FROM wp_blogs b
WHERE b.deleted = 0;
-- Note: Dynamic table names require procedural code

Get users for a specific site

SELECT u.* 
FROM wp_users u
JOIN wp_usermeta um ON u.ID = um.user_id
WHERE um.meta_key = 'wp_2_capabilities';

WordPress API Functions

• get_sites( $args ) – Get sites
• get_site( $site_id ) – Get single site
• get_blog_details( $blog_id ) – Get site details
• get_current_blog_id() – Current site ID
• switch_to_blog( $blog_id ) – Switch context
• restore_current_blog() – Restore context
• is_multisite() – Check if multisite
• get_network_option( $network_id, $option ) – Get sitemeta
• update_network_option( $network_id, $option, $value ) – Update sitemeta
• get_blog_option( $blog_id, $option ) – Get site option
• add_blog_meta( $blog_id, $key, $value ) – Add blogmeta
• get_blog_meta( $blog_id, $key, $single ) – Get blogmeta

Table Prefix in Multisite

global $wpdb;

// Current site prefix (e.g., "wp_" or "wp_2_")
$wpdb->prefix;

// Base prefix (always "wp_")
$wpdb->base_prefix;

// Get prefix for specific site
$wpdb->get_blog_prefix( $blog_id );