Question

我需要创建一个触发器，根据其他列值计算一个列值。数据库有点非规范化以获得更高的性能。（规范化不是这个问题的问题）。

问题是我想设置computed_address值的值，如果我在其中放置一个常量就可以了。但似乎这些If条款不起作用，我只是看不出问题。

以下是触发器代码。非常感谢你！

DELIMITER $$

USE `nth_poi_new_3`$$

DROP TRIGGER /*!50032 IF EXISTS */ `poi_address_creator`$$

CREATE
    /*!50017 DEFINER = 'root'@'localhost' */
    TRIGGER `poi_address_creator` BEFORE INSERT ON `poi` 
    FOR EACH ROW BEGIN
    DECLARE full_address VARCHAR(255);
    DECLARE country_string VARCHAR(100);
    DECLARE region_string VARCHAR(100);
    DECLARE town_string VARCHAR(100);
    DECLARE address_string VARCHAR(100);

    IF NEW.address <> '' THEN   
        SET full_address = CONCAT(NEW.address, ",");

    END IF;
    IF NEW.town_name IS NOT NULL THEN
        SET full_address = CONCAT(full_address, NEW.town_name, ",");
    ELSEIF NEW.town_id IS NOT NULL THEN
        SELECT NAME INTO town_string FROM town WHERE town.town_id = NEW.town_id LIMIT 1;
        SET full_address = CONCAT(full_address, town_string, ",");
    END IF;

    IF NEW.region_name IS NOT NULL THEN
        SET full_address = CONCAT(full_address, NEW.region_name, ",");
    ELSEIF NEW.region_id IS NOT NULL THEN
        SELECT NAME INTO region_string FROM region WHERE region.region_id = NEW.region_id LIMIT 1;
        SET full_address = CONCAT(full_address, region_string, ",");
    END IF;

    IF NEW.country_name IS NOT NULL THEN
        SET full_address = CONCAT(full_address, NEW.country_name, ",");
    ELSEIF NEW.country_id IS NOT NULL THEN
        SELECT NAME INTO country_string FROM country WHERE country.country_id = NEW.country_id LIMIT 1;
        SET full_address = CONCAT(full_address, country_string, ",");
    END IF;

    SET NEW.computed_address = full_address;

    END;
$$

DELIMITER ;

Answer 1

位于触发器代码的底部

END; 
$$

DELIMITER ;

应该是

END$$

DELIMITER ;

Answer 2

嘿只是回答。我必须先初始化full_address变量。我刚刚做了这个：

DECLARE full_address VARCHAR(255);

但声明之后它还需要初始化：

SET full_address="";

MySql触发器不会计算

2 个答案: