How to get the result of $wpdb ->query to know if it was successful

Solution:

$modif_doc_bdd = $wpdb->query($wpdb->prepare("UPDATE `mod114_frmt_form_entry_meta_copie` SET  `meta_value` = '$ValeurChampModif' WHERE `mod114_frmt_form_entry_meta_copie`.`meta_id` =    $Champ_id;"));
 
if ( false === $modif_doc_bdd ) {
    // There was an error.
} else {
    // No error. You can check updated to see how many rows were changed.
}