ORA-24344：编译错误成功。触发顶点

Question

我正在尝试在oracle apex中创建一个触发器，它将选择我在UniversityRefNo列中的所有数据，并且不允许用户输入已存在的值。但是，我一直收到这个错误："ORA-24344: success with compilation error."如果有人能告诉我，我做错了哪个会很棒。

CREATE TABLE VOLUNTEER(
Volunteer_id         NUMBER(5) PRIMARY KEY,    
Title                VARCHAR2(5),    
VolName              VARCHAR2(30),   
UniversityRefNo      VARCHAR2(10),    
Address_Line_1       VARCHAR2(30),   
Address_Line_2       VARCHAR2(12),    
PostCode             VARCHAR2(12),    
Mobile_Number        NUMBER(12),    
Home_Number          NUMBER(12),    
Email                VARCHAR2(25),    
Ethnic_Group         VARCHAR2(10),    
VolunteerType        VARCHAR2(10),   
Register_Disable     VARCHAR2(3),  
Gender               VARCHAR2(1),  
Medical_Details      VARCHAR2(20),   
PassPortNumber       NUMBER(10),   
Nationality          VARCHAR2(10),   
Passport_Expiry_Date DATE,    
Date_of_Birth        DATE,   
Course_Name          VARCHAR2(20),   
Course_Year          VARCHAR2(10),   
Area_of_work         VARCHAR2(15),    
StaffManagerName     VARCHAR2(20),    
StaffManagerEmail    VARCHAR2(20),    
StaffManagerPhone    VARCHAR2(12));   

CREATE or replace trigger unirefnoTrigger    
before insert or update of UniversityRefNo ON VOLUNTEER for each row    
begin    
SELECT UniversityRefNo from VOLUNTEER    
if(UniversityRefno = :new.UniversityRefNo) then raise application error(UniversityRefNO || :new.UniversityRefNo || 'already exists');   
end if;    
end;

Answer 1

如果你想让大学的RefNo列独一无二而你不需要制作一个触发器就可以简单地创建一个这样的唯一约束：

ALTER TABLE VOLUNTEER 
ADD CONSTRAINT UniversityRefNo_UK UNIQUE (UniversityRefNo);

以下是学习目的，您可以创建触发器来执行相同的操作，但我不建议您使用它。

CREATE or replace trigger unirefnoTrigger
before insert or update of UniversityRefNo ON VOLUNTEER for each row
university_count number;
begin
SELECT count(*) into university_count from VOLUNTEER where UniversityRefno=:new.UniversityRefNo;
if university_count<>0 then 
raise application error(-20000, :new.UniversityRefNo || ' already exists');
end if;
end;