Question

我正在尝试根据下面链接上的图片上的问题创建触发器。但我正在努力处理重复更新并处理插入和更新时的最大字符长度。这是我的解决方案。

CREATE OR REPLACE TRIGGER check_author
BEFORE UPDATE OR INSERT  ON bk_author
FOR EACH ROW
DECLARE
v_authorid bk_author.authorid%type;
BEGIN
IF UPDATING THEN
IF LENGTH(:NEW.fname) > 10 THEN
RAISE_APPLICATION_ERROR(-20004,'Author name cannot exceed 10 characters');
END IF;
ELSIF INSERTING THEN
SELECT authorid
INTO v_authorid
FROM bk_author
WHERE authorid = :NEW.authorid;
RAISE_APPLICATION_ERROR(-20003,'Author id already existing cannot be added');
IF LENGTH(:NEW.fname) > 10 THEN
RAISE_APPLICATION_ERROR(-20004,'Author name cannot exceed 10 characters');
END IF;

END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE('Author '||:NEW.authorid||' added');
END;
/

Answer 1

您不会检查条件以提出有关重复的错误，无论数据库中是否有ID，它都会执行。

你应该在它之前添加IF

类似

ELSIF INSERTING THEN
SELECT authorid
INTO v_authorid
FROM bk_author
WHERE authorid = :NEW.authorid;
IF v_authorid is not null then
    RAISE_APPLICATION_ERROR(-20003,'Author id already existing cannot be 
  added');
 end if;

Answer 2

尝试下面的代码，它应该适合你。

CREATE OR REPLACE TRIGGER check_author
BEFORE UPDATE OR INSERT  ON bk_author
FOR EACH ROW
DECLARE
v_authorid number;
BEGIN
IF UPDATING THEN
IF LENGTH(:NEW.fname) > 10 THEN
RAISE_APPLICATION_ERROR(-20004,'Author name cannot exceed 10 characters');
END IF;
ELSIF INSERTING THEN
SELECT count(authorid) INTO v_authorid
FROM bk_author
WHERE authorid = :NEW.authorid;

DBMS_OUTPUT.PUT_LINE('Author id already existing cannot be added');
RAISE;
IF LENGTH(:NEW.fname) > 10 THEN
DBMS_OUTPUT.PUT_LINE('Author name cannot exceed 10 characters');
RAISE;
END IF;

END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE('Author '||:NEW.authorid||' added');
END;
/

在PL / SQL oracle中创建触发器9

2 个答案: