Remove all users from Wordpress Multisite that do not belong to other sites

remove.sql

SET @site_id = 1;

SELECT user_id
FROM wp_usermeta
WHERE meta_key = CONCAT('wp_', @site_id, '_capabilities')
    AND meta_value LIKE 'a:1:{s%'
HAVING user_id NOT IN (
    SELECT user_id
    FROM wp_usermeta
    WHERE meta_key LIKE CONCAT('wp_', @site_id, '_capabilities')
    AND meta_value LIKE 'a:1:{s%'
    GROUP BY user_id
    HAVING COUNT(user_id) > 1
    ORDER BY user_id
);

DELETE FROM wp_users
WHERE id IN (
    SELECT user_id
    FROM wp_usermeta
    WHERE meta_key = CONCAT('wp_', @site_id, '_capabilities')
        AND meta_value LIKE 'a:1:{s%'
    HAVING user_id NOT IN (
        SELECT user_id
        FROM wp_usermeta
        WHERE meta_key CONCAT('wp_', @site_id, '_capabilities')
        AND meta_value LIKE 'a:1:{s%'
        GROUP BY user_id
        HAVING COUNT(user_id) > 1
        ORDER BY user_id
    )
);

SELECT umeta_id FROM wp_usermeta
WHERE NOT EXISTS (
  SELECT ID FROM wp_users WHERE wp_usermeta.user_id = wp_users.ID
);

DELETE FROM wp_usermeta
WHERE NOT EXISTS (
  SELECT ID FROM wp_users WHERE wp_usermeta.user_id = wp_users.ID
);