行受影响 是什么意思

CREATE TABLE  Student
(
  Sno   char(7) PRIMARY KEY , 
  Sname nchar(5)  NOT NULL   ,
  Sex   nchar(1) DEFAULT '男' ,
  Sage  tinyint  check( Sage>=15 ANd Sage <=45),
  Sdept nvarchar(20)        ---可变长度的统一编码nverchar
)
GO
INSERT INTO Student VALUES ('1','李明','男',20,N'计算机系')
INSERT INTO Student VALUES ('2','张然','女',19,N'经管系' )
INSERT INTO Student VALUES ('3','许晴','女',18,N'电子系')

CREATE TABLE Course
(
  Cno char(7)  PRIMARY KEY ,
  Cname nvarchar(20) not null ,
  Credit numeric(3,1) check(credit>=0)  --numeric(p,,s) p 为精度，是为小数位个数
)

INSERT INTO Course  VALUES('1', 'SQL Server',4)
INSERT INTO Course  VALUES('2'    ,'VB',3)
INSERT INTO Course  VALUES('3','专业英语',2)

CREATE TABLE SC
(
  Sno  char(7) not null ,
  Cno  char(7)  not null ,
  Grade tinyint ,
 PRIMARY KEY (Sno, Cno),    --定义主码约束
 FOREIGN KEY (Sno) REFERENCES Student(Sno) , --定义外码约束并关联student
 FOREIGN KEY (Cno) REFERENCES Course(Cno)    
)
INSERT INTO SC  VALUES ('1','1',90)
INSERT INTO SC  VALUES ('2','2',76)
INSERT INTO SC  VALUES ('2','1',85)
INSERT INTO SC  VALUES ('3','3',70)
Go