SQL语句，表与表之间的引用

constraint 外键表名_id_fk foreign key (外键字段名) references 主表名(主表id)

create table FirNav

(

    id int primary key identity(1,1) not null,

    navName varchar(10) not null,

);



create table SecNav

(

    id int primary key identity(1,1) not null,

    navName varchar(10) not null,

    firId int ,

    constraint SecNav_id_fk foreign key (firId) references FirNav(id)

);



create table ThirdNav

(

    id int primary key identity(1,1) not null,

    navName varchar(10) not null,

    secId int,

    constraint ThirdNav_id_fk foreign key (secId) references SecNav(id)

);