Activar Cuenta

Notice: Undefined variable: userid in /home/poolcent/public_html/ on line 219

Error en la base de datos de WordPress: [You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'AND meta_key='activation_key'' at line 1]
SELECT meta_value FROM w47fa_usermeta WHERE user_id= AND meta_key='activation_key'

Activation key is missing
There is something wrong with the username