这个MySQL触发器有什么问题?

时间:2014-01-13 16:59:35

标签: mysql sql triggers

我正在尝试编写一个触发器,将表中的所有条目从1到10排列(最大值具有等级10,最小值具有等级1,所有其他值都被赋予其间的整数值)。这是触发器代码:

DELIMITER $$
CREATE TRIGGER risks_before_insert
BEFORE INSERT ON risks
FOR EACH ROW
BEGIN

DECLARE max_cost double; #previous maximum expected_cost in project
DECLARE min_cost double; #previous minimum expected_cost in project
DECLARE slope double; #slope for prioritizing functioN

SELECT MAX(expected_cost), MIN(expected_cost) INTO max_cost, min_cost FROM view_risks; #GET EXTREME VALUES FROM TABLE, STORE IN MEMORY

/*
Update Priority Monetary Rankings
*/
IF (max_cost IS NULL OR min_cost IS NULL) THEN #check for empty table
    SET NEW.priority_monetary = 10;
ELSE IF ((NEW.expected_cost <= max_cost) AND (NEW.expected_cost >= min_cost)) THEN #NEW VALUE DOES NOT CHANGE TABLE EXTREMES
    IF (max_cost – min_cost = 0) THEN
        SET NEW.priority_monetary = 10;
    ELSE
        SET slope = 9 / (max_cost – min_cost);
        SET NEW.priority_monetary = slope * (NEW.expected_cost - min_cost) + 1;
    END IF;
ELSE IF (NEW.expected_cost > max_cost) THEN
    SET NEW.priority_monetary = 10;
    SET slope = 9 / (NEW.expected_cost – min_cost);
    UPDATE TABLE risks SET priority_monetary = slope * (expected_cost - min_cost) + 1;
ELSE #NEW VALUE CORRESPONDS TO A MINIMUM
    SET NEW.priority_monetary = 1;
    SET slope = 9 / (max_cost – NEW.expected_cost);
    UPDATE TABLE risks SET priority_monetary = slope * (expected_cost – NEW.min_cost) + 1;
END IF;
END $$
DELIMITER ;

但是,我收到以下错误:

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '– min_cost); SET NEW.priority_monetary = slope * (NEW.expected_cost - min_cost' at line 22

任何人都可以解释什么是错的吗?供您参考,我的排名算法由以下函数描述,常量为maxval和minval:

  

Rank(x)= 1 + slope(x - minval),其中slope = 9 /(maxval - minval)。

2 个答案:

答案 0 :(得分:1)

你应该检查一个超出范围的例外。它永远不应该等于0.如果它确实会查询失败并填满数据库。

在将maxval设置为minval <之前,您应该检查maxval - minval0以确保slope不等于9/(maxval - minval) / p>

如果你运行这个

SET slope = 9 / (max_cost – min_cost);

并尝试将slope设置为9/0它会崩溃。

答案 1 :(得分:1)

我不熟悉触发器,但我认为您的问题出在SET声明中。

我在想你不能设置NEW.priority_monetary

我之前没有看到任何类似SQL的语法,但我仍然是游戏的新手,但我猜你如果放弃NEW.而只是设置priority_monetary那么错误可能会消失