引用完整性

##引用完整性

学生表

   Id

   名字

   性别

 

成绩表

   Id

   学生ID

  成绩

 

Create table stu7（

   Id int primary key;

   Name varchar(50)

)

Create table score(

      Id int primary key,

      Sid int,

      Score double,

      Constraint as foreign key(sid) references stu7(id)

)

 

Insert into stu7(id,name) values(1,”zsf”);

Insert into score(id,sid,score) values(1,1,90);

 

ERROR 1452 (23000):Cannot add or update a child

Row:a foreign key constraint fails (‘db_0402’,’score’;

 CONSTRAINT ‘aa’FOREIGN KEY (‘sid’)REFERENCES’stu7’(id))