协助创建触发器

Question

大家好，我需要在 ORACLE 10g 中创建一个触发器，以确保无法输入在birthDate 之前的 deathDate。我真的在这方面苦苦挣扎，请你提供支持，谢谢你好心的人。

我的方案是：

Actor (actorID, lastName, firstName, middleName, suffix, gender, birthDate, deathDate)
Movie (movieID, title, year, company, totalNoms, awardsWon, DVDPrice, discountPrice)
Quote (quoteID, quote)
Role (roleID ,roleName ,gender ,actorID* ,movieID*) 
RoleQuote (roleID*, quoteID*)

谢谢

如果您需要更多信息，请询问

我的关系约束是：

CONSTRAINT_NAME                C                                                
------------------------------ -                                                
QUOTE_FK                       R                                                
ROLE_FK                        R                                                
MOVIE_ROLE_FK                  R                                                
ACTOR_ROLE_FK                  R                                                
ACTORID                        P                                                
MOVIEID                        P                                                
QUOTEID                        P                                                
ROLEID                         P                                                
ROLEQUOTEID                    P       

Relationships:

ALTER TABLE Role ADD CONSTRAINT ACTOR_ROLE_FK FOREIGN KEY (actorID) REFERENCES Actor (actorID);
ALTER TABLE Role ADD CONSTRAINT MOVIE_ROLE_FK FOREIGN KEY (movieID) REFERENCES Movie (movieID);
ALTER TABLE RoleQuote ADD CONSTRAINT Role_FK FOREIGN KEY (roleID) REFERENCES Role (roleID);
ALTER TABLE RoleQuote ADD CONSTRAINT Quote_FK FOREIGN KEY (quoteID) REFERENCES Quote (quoteID);

Answer 1

这种约束应该作为CHECK 约束来实现

ALTER TABLE actor
  ADD CONSTRAINT chk_birth_before_death CHECK( birthDate < deathDate );

如果您确实需要通过触发器强制执行约束（这会更慢并且需要更多工作）

CREATE OR REPLACE TRIGGER check_death_date
  AFTER INSERT OR UPDATE ON actor
  FOR EACH ROW
BEGIN
  IF( :new.birthDate > :new.deathDate )
  THEN
    RAISE_APPLICATION_ERROR( -20001, 'Birth date cannot be later than death date.' );
  END IF;
END;