我在触发前更新有问题答案

【问题标题】：I have a problem with an UPDATE BEFORE TRIGGER我在触发前更新有问题
【发布时间】：2021-12-02 18:21:09
【问题描述】：

我有以下表格：

CREATE TABLE Categorie
(categ_id NUMBER(5,0),
tip VARCHAR2(20));

CREATE TABLE Reteta
(reteta_id NUMBER(3),
nume VARCHAR2(100),
descriere VARCHAR2(200),
categ_id NUMBER(3,0),
vegetariana VARCHAR2(1) CHECK (vegetariana IN ('D','N')),
timp_preparare NUMBER(20,1),
portii NUMBER(3,1));

CREATE TABLE Set_ingrediente
(reteta_id NUMBER(3,0),
ingred_id NUMBER(3,0), 
cantitate NUMBER(5,2), 
um VARCHAR2(10) NOT NULL CHECK (um IN ('gr','ml','buc','lingurita','cana')), 
comentarii VARCHAR2(100)
);

CREATE TABLE Ingredient 
(ingred_id NUMBER(3,0), 
ingredient VARCHAR2(30));

以及以下主键/外键：

ALTER TABLE Categorie
MODIFY (categ_id CONSTRAINT categ_id_pk PRIMARY KEY NOT NULL);

ALTER TABLE Reteta
MODIFY(CONSTRAINT reteta_id_pk PRIMARY KEY (reteta_id));

ALTER TABLE Ingredient
MODIFY(CONSTRAINT ingred_id_pk PRIMARY KEY (ingred_id));

ALTER TABLE Set_ingrediente
MODIFY( CONSTRAINT reteta_id_fk FOREIGN KEY (reteta_id) REFERENCES Reteta(reteta_id) ON DELETE CASCADE);

ALTER TABLE Set_ingrediente
MODIFY( CONSTRAINT ingred_id_fk FOREIGN KEY (ingred_id) REFERENCES Ingredient(ingred_id) ON DELETE CASCADE);

我必须编写一个触发器：如果食谱使用“油”成分，请确保素食栏不能更改。这是我尝试过的触发器，但它不起作用：

CREATE OR REPLACE TRIGGER tr_oil BEFORE UPDATE
ON Reteta
FOR EACH ROW BEGIN
DECLARE
 ingredient_var ingredient.ingredient%type;
 SELECT ingredient
 INTO ingredient_var
 FROM Ingredint
 WHERE ingred_id=
 (SELECT ingred_id
 FROM Set_ingrediente
 WHERE reteta_id=NEW.reteta_id);
 IF ingredient_var='oil' THEN  
SET NEW.vegetariana = OLD.vegetariana;
END IF;
END;

【问题讨论】：

标签： oracle plsql triggers

【解决方案1】：

这太奇怪了；直到触发代码，您发布的所有内容都完美工作，所以我无法想象当涉及到充满错误的触发器时出了什么问题（错位begin，无效的表名，缺少冒号使用:new 伪记录，...）。好像两个不同的人编写了您发布的两段代码。

无论如何：

SQL> CREATE OR REPLACE TRIGGER tr_oil
  2    BEFORE UPDATE ON Reteta
  3    FOR EACH ROW
  4  DECLARE
  5    ingredient_var ingredient.ingredient%type;
  6  BEGIN
  7    SELECT ingredient
  8      INTO ingredient_var
  9      FROM Ingredient
 10      WHERE ingred_id = (SELECT ingred_id
 11                         FROM Set_ingrediente
 12                         WHERE reteta_id = :NEW.reteta_id);
 13
 14    IF ingredient_var='oil' THEN
 15       :NEW.vegetariana := :OLD.vegetariana;
 16     END IF;
 17  END;
 18  /

Trigger created.

SQL>

【讨论】：