sql - 在 SQL 表创建过程中还有其他方法可以创建约束吗？

Question

假设我有以下 SQL 语句，使用 Oracle:

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,
    dob     date ,
    firstName   varchar2(20),
    lastName    varchar2(20),
    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department和faculty之间存在chair关系的递归引用，所以department中chair的外键约束只有在faculty表定义后才能定义。必须在使用 alter table 语句定义 faculty 之后添加约束。

是否有任何其他方法可以做到这一点，以某种方式自动创建约束，从而消除 alter table 语句？

Answer 1

您可以使用 create schema 来做到这一点声明:

create schema authorization [schema name]
create table department 
(   code      varchar2(3) primary key,
    name      varchar2(40)  not null,
    chair     varchar2(11),
    constraint departmentChairFk foreign key(chair) references facultyStaff(staffId) on delete set null
)
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,
    dob     date ,
    firstName   varchar2(20),
    lastName    varchar2(20),
    status      varchar(10),
    major       varchar(3),
constraint statusValue check (status in ('Freshman', 'Sophomore', 'Junior', 'Senior',  'Graduate')),
    constraint studentMajorFk foreign key (major) references department (code)
);