MySQL 触发器 IF 语句错误（不会创建）

Question

我想像这样创建触发器，如果学生的分数高于这样其他列的分数将自动插入值（字母）

 DELIMITER |
    CREATE TRIGGER N_Angka BEFORE INSERT ON nilai
    FOR EACH ROW
    BEGIN
        IF nilai_angka <= 50 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'C-';
            ELSE IF nilai_angka < 55 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'C';
            ELSE IF nilai_angka < 59 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'C+';
            ELSE IF nilai_angka <= 60 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'B-';
            ELSE IF nilai_angka < 75 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'B';
            ELSE IF nilai_angka <= 80 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'B+';
            ELSE IF nilai_angka <= 85 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'A-';
            ELSE IF nilai_angka <= 90 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'A';
            ELSE IF nilai_angka <= 99 THEN
                UPDATE nilai SET NEW.nilai_huruf = 'A+';
            ELSE
                UPDATE nilai SET NEW.nilai_huruf = 'S';
            END IF;
    END |
    DELIMITER ;

它说第26行有错误它在

END IF;

有人可以为我解释并提供一些解决方案吗

Answer 1

您不能使用 UPDATE 但您可以根据 NEW.nilai_angka 设置 NEW.nilai_huruf 的值，因为它是一个 BEFORE 触发器。

使用CASE表达更简洁

因为它现在是单语句触发器，所以您不再需要使用 BEGIN...END 块。

CREATE TRIGGER N_Angka
BEFORE INSERT ON nilai
FOR EACH ROW
  SET NEW.nilai_huruf = CASE 
    WHEN NEW.nilai_angka <=50              THEN 'C-'
    WHEN NEW.nilai_angka BETWEEN 51 AND 54 THEN 'C'
    WHEN NEW.nilai_angka BETWEEN 55 AND 58 THEN 'C+'
    WHEN NEW.nilai_angka BETWEEN 59 AND 60 THEN 'B-'
    WHEN NEW.nilai_angka BETWEEN 61 AND 74 THEN 'B'
    WHEN NEW.nilai_angka BETWEEN 75 AND 80 THEN 'B+'
    WHEN NEW.nilai_angka BETWEEN 81 AND 85 THEN 'A-'
    WHEN NEW.nilai_angka BETWEEN 86 AND 90 THEN 'A'
    WHEN NEW.nilai_angka BETWEEN 91 AND 99 THEN 'A+'
    ELSE 'S' END;

这是一个SQLFiddle演示

您很可能想创建一个免费的 BEFORE UPDATE 触发器。此时将逻辑提取到函数中是有意义的

CREATE FUNCTION angka_huruf(_angka INT)
RETURNS VARCHAR(2) DETERMINISTIC
RETURN CASE 
  WHEN _angka <=50              THEN 'C-'
  WHEN _angka BETWEEN 51 AND 54 THEN 'C'
  WHEN _angka BETWEEN 55 AND 58 THEN 'C+'
  WHEN _angka BETWEEN 59 AND 60 THEN 'B-'
  WHEN _angka BETWEEN 61 AND 74 THEN 'B'
  WHEN _angka BETWEEN 75 AND 80 THEN 'B+'
  WHEN _angka BETWEEN 81 AND 85 THEN 'A-'
  WHEN _angka BETWEEN 86 AND 90 THEN 'A'
  WHEN _angka BETWEEN 91 AND 99 THEN 'A+'
  ELSE 'S' END;

然后在两个触发器中重复使用它

CREATE TRIGGER N_Angka
BEFORE INSERT ON nilai
FOR EACH ROW
  SET NEW.nilai_huruf = angka_huruf(NEW.nilai_angka);

CREATE TRIGGER N_Angka2
BEFORE UPDATE ON nilai
FOR EACH ROW
  SET NEW.nilai_huruf = angka_huruf(NEW.nilai_angka);

这是一个SQLFiddle演示

现在，您也可以完全放弃触发器和 nilai_huruf 列，只要在获取记录时就使用该函数

SELECT nilai_angka, angka_huruf(nilai_angka) nilai_huruf
  FROM nilai;

这是一个SQLFiddle演示

Answer 2

DELIMITER $$
CREATE TRIGGER N_Angka BEFORE INSERT ON nilai
FOR EACH ROW
BEGIN
    IF NEW.nilai_angka <= 50 THEN
            BEGIN
                SET NEW.nilai_huruf = 'C-';
                END;
        ELSEIF NEW.nilai_angka < 55 THEN
            BEGIN
                SET NEW.nilai_huruf = 'C';
                END;
        ELSEIF NEW.nilai_angka < 59 THEN
            BEGIN
                SET NEW.nilai_huruf = 'C+';
                END;
        ELSEIF NEW.nilai_angka <= 60 THEN
            BEGIN
                SET NEW.nilai_huruf = '-B';
                END;
        ELSEIF NEW.nilai_angka < 75 THEN
            BEGIN
                SET NEW.nilai_huruf = 'B';
                END;
        ELSEIF NEW.nilai_angka <= 80 THEN
            BEGIN
            SET NEW.nilai_huruf = 'B+';
                END;
        ELSEIF NEW.nilai_angka <= 85 THEN
            BEGIN
            SET NEW.nilai_huruf = 'A-';
                END;
        ELSEIF NEW.nilai_angka <= 90 THEN
            BEGIN
            SET NEW.nilai_huruf = 'A';
                END;
        ELSEIF NEW.nilai_angka <= 99 THEN
            BEGIN
            SET NEW.nilai_huruf = 'A+';
                END;
        ELSEIF NEW.nilai_angka = 100 THEN
            BEGIN
            SET NEW.nilai_huruf = 'S';
                END; 
                END IF;
END$$
DELIMITER ;

这就是答案我更改触发器上的事件

MySQL 触发器 IF 语句错误（不会创建）

MySQL Trigger IF Statement Error (Won't Create)

mysql

triggers