觸發器/程序幫助

Question

create table student 
(spnr VARCHAR(5) PRIMARY KEY, 
sname VARCHAR(10), 
saddress VARCHAR(10), 
stel VARCHAR(10)) 

create table course 
    (ccode VARCHAR(5) PRIMARY KEY, 
    cname VARCHAR(10), 
    caddress VARCHAR(10), 
    points int) 

create table studies 
    (id  int  PRIMARY KEY, 
    spnr VARCHAR(5) NOT NULL, 
    ccode VARCHAR(5) NOT NULL, 
    result int,  
    CONSTRAINT STUDIES_SPNR_FK FOREIGN KEY(spnr) REFERENCES student(spnr), 
    CONSTRAINT STUDIES_CCODE_FK FOREIGN KEY(ccode) REFERENCES course(ccode)) 

create trigger t1 on course 
after update,insert 
as 
    print 'inside trigger'; 
    select i.ccode from inserted i, deleted d 
    where i. ccode = d. ccode 

create procedure what (@tableName varchar(10)) 
as 
begin 

    declare @name varchar(20); 

    declare c cursor for 
    select column_name 
    from information_schema.columns 
    where table_name = @tableName; 
    open c; 
    fetch c into @name; 
    while @@fetch_status = 0 begin 
     print 'name:' + @name; 
     fetch c into @name; 
    end 

    close c; 
    deallocate c; 
end; 

當運行：顯示

begin transaction 
insert into course values('K1','data1','lund',5); 
update course 
set cname ='informatik'; 
commit 

以下消息：

inside trigger 

(0 row(s) affected) 

(1 row(s) affected) 
inside trigger 

(1 row(s) affected) 

(1 row(s) affected) 

最後，爲什麼1行受影響節目的2倍到底？當它只在一個位置將cname更改爲「informatic」時？

Answer 1

一個「1行受影響」來自UPDATE，另一個來自觸發器中的SELECT。嘗試從觸發器中刪除SELECT，您應該只會看到一個「受影響的行」。