Made some minor db changes at SF's request. I ported over the "Linked titles" field created for convenience in the backup db to the main db, since this seems useful; and I also re-implemented the triggers which create the own_desc lookup field in the owners table, using this (tested in dev, implemented in live, and actually run in four steps for caution's sake):

/* This file rebuilds the existing triggers for the own_desc field. */  
   
DELIMITER $$
   
/* First delete the existing triggers. */

DROP TRIGGER IF EXISTS `own_desc_insert`$$

DROP TRIGGER IF EXISTS `own_desc_update`$$

/* Now recreate the contents of the own_desc field. */
   
   UPDATE `owners` SET `own_desc` = CASE
      WHEN (LENGTH(`own_surname`) > 0 AND LENGTH(`own_forenames`) > 0 AND LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_surname`,_utf8', ',`own_forenames`,_utf8' : ',`own_street_num`,_utf8', ',`own_street`)
      WHEN (LENGTH(`own_surname`) > 0 AND LENGTH(`own_forenames`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_surname`,_utf8', ',`own_forenames`,_utf8' : ',`own_street`)
      WHEN (LENGTH(`own_surname`) > 0 AND LENGTH(`own_forenames`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_surname`,_utf8', ',`own_forenames`,_utf8' : (no address)')
      WHEN (LENGTH(`own_surname`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_surname`,_utf8' (no forenames or address)')
      WHEN (LENGTH(`own_institution_name`) > 0 AND LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_institution_name`,_utf8' : ',`own_street_num`,_utf8', ',`own_street`)
      WHEN (LENGTH(`own_institution_name`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_institution_name`,_utf8' : ',`own_street`)
      WHEN (LENGTH(`own_institution_name`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',`own_institution_name`,_utf8' : (no address)')
      WHEN (LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',_utf8' : (no name): ',`own_street_num`,_utf8', ',`own_street`)
      WHEN (LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_owner_id`,_utf8'. ',_utf8' : (no name or street number): ',`own_street`)
      ELSE 
          concat(`own_owner_id`,_utf8'. ',_utf8'(no name or address)')
      END; $$

/* Now recreate the triggers. */
    
CREATE TRIGGER `own_desc_insert` BEFORE INSERT ON `owners`
  FOR EACH ROW BEGIN
	SET NEW.`own_desc` = CASE
	  WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : (no address)')
      WHEN (LENGTH(NEW.`own_surname`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8' (no forenames or address)')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_institution_name`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_institution_name`,_utf8' : ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_institution_name`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_institution_name`,_utf8' : (no address)')
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',_utf8' : (no name): ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',_utf8' : (no name or street number): ',NEW.`own_street`)
      ELSE 
          concat(NEW.`own_owner_id`,_utf8'. ',_utf8'(no name or address)')
      END;
  END; $$
  

  
CREATE TRIGGER `own_desc_update` BEFORE UPDATE ON `owners`
  FOR EACH ROW BEGIN
	SET NEW.`own_desc` = CASE
	  WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : (no address)')
      WHEN (LENGTH(NEW.`own_surname`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_surname`,_utf8' (no forenames or address)')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_institution_name`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_institution_name`,_utf8' : ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_institution_name`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',NEW.`own_institution_name`,_utf8' : (no address)')
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',_utf8' : (no name): ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`)
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_owner_id`,_utf8'. ',_utf8' : (no name or street number): ',NEW.`own_street`)
      ELSE 
          concat(NEW.`own_owner_id`,_utf8'. ',_utf8'(no name or address)')
      END;
  END; $$

DELIMITER ;