您需要为此使用元查询。

$meta_query_args = array(
    array(
        \'key\'     => \'access_code\',
        \'value\'   => \'abc\',
        \'compare\' => \'=\'
    )
);

$args =  array(
  \'meta_query\'   => $meta_query_args
);

$users = get_users( $args );

// User Loop
foreach ( $users as $user ) {
  update_user_meta( $user->ID, \'association\', \'XYZ Corporation\');
}