假设我使用Oracle有以下sql语句：
drop table department cascade constraints;
drop table facultyStaff cascade constraints;
drop table student cascade constraints;
drop table campusClub cascade constraints;
drop table studentClub cascade constraints;
create table department
( code varchar2(3) primary key,name varchar2(40) not null,chair varchar2(11));
create table facultyStaff
( staffID varchar2(5) primary key,dob date,firstName varchar2(20),lastName varchar2(20),rank varchar2(10),deptCode varchar2(3),constraint rankValue check (rank in ('Assistant','Associate','Full','Emeritus')),constraint facultyDeptFk foreign key (deptCode) references department (code));
create table student
( studentId varchar2(5) primary key,status varchar(10),major varchar(3),constraint statusValue check (status in ('Freshman','Sophomore','Junior','Senior','Graduate')),constraint studentMajorFk foreign key (major) references department (code));
alter table department
add constraint departmentChairFk foreign key(chair) references facultyStaff(staffId) on delete set null;
由于主席与教职员之间存在主席关系的递归参考,因此在定义教师表之前,无法定义部门主席的外键约束.在使用alter table语句定义faculty之后,必须添加约束.
解决方法
您可以使用
create schema语句执行此操作：
create schema authorization [schema name] create table department ( code varchar2(3) primary key,chair varchar2(11),constraint departmentChairFk foreign key(chair) references facultyStaff(staffId) on delete set null ) create table facultyStaff ( staffID varchar2(5) primary key,constraint facultyDeptFk foreign key (deptCode) references department (code) ) create table student ( studentId varchar2(5) primary key,constraint studentMajorFk foreign key (major) references department (code) );
