就我个人而言，如果我需要编写一个执行指定操作并返回结果集的过程，我会这样编写：

DELIMITER $$

CREATE DEFINER=`user`@`localhost` PROCEDURE `set_address`
(IN `patient_street`            VARCHAR(128)
,IN `patient_city`              VARCHAR(45)
,IN `patient_post_code`         VARCHAR(45)
,IN `patient_state_or_province` VARCHAR(45)
,IN `patient_country`           VARCHAR(45)
)
NOT DETERMINISTIC SQL SECURITY DEFINER
BEGIN
  DECLARE li_address_id BIGINT DEFAULT NULL;
  -- check for existing row and get address_id
  SELECT a.address_id
    INTO li_address_id
    FROM address a
   WHERE a.street    = patient_street
     AND a.city      = patient_city
     AND a.post_code = patient_post_code
     AND a.country   = patient_country
   LIMIT 1 ;
  -- if we didn't find a matching row
  IF li_address_id IS NULL THEN
    -- add a row and get the new address_id
    INSERT INTO address (street, city, post_code, state_or_province, country) VALUES
    (patient_street, patient_city, patient_post_code, patient_state_or_province, patient_country);
    SELECT LAST_INSERT_ID() INTO li_address_id;
  END IF;

  -- return address_id (either found existing row, or newly added row) as a resultset
  SELECT li_address_id AS address_id;
END$$

DELIMITER ;

如果存在一行，我们不需要运行两行 SELECT 声明。我们可以对该行进行检查，并使用单个 SELECT .
如果没有得到匹配的行，则插入一行，并检索自动递增id。
在任何一种情况下（找到的行或添加的行），都将地址\u id作为结果集返回。同样，我们可以用一个select语句，而不是两个不同的语句。
对我来说，限制返回resultsets的位置数和查询数据库的次数更有意义。