触发器/程序帮助

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; 

当运行：显示

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) 

最后，为什么1行受影响节目的2倍到底？当它只在一个位置将cname更改为“informatic”时？

Answer 1

一个“1行受影响”来自UPDATE，另一个来自触发器中的SELECT。尝试从触发器中删除SELECT，您应该只会看到一个“受影响的行”。