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create table title_copy(
id number(3) not null,
t_id number(3) not null,
status char(9) default '未借出' constraint title_copy_status check(status in('已借出','未借出') ) ,
constraint title_copy_primary primary key(id),
constraint title_copy_foreign foreign key(t_id) references title(id)
);
alter table title_copy modify status constraint title_copy_status check(status in('已借出','未借出')) not null ;
alter table title_copy modify status constraint title_copy_status not null ;
--方法1:
create table title_copy(
id number(3) not null,
t_id number(3) not null,
status char(9) default '未借出' not null,
constraint title_copy_primary primary key(id),
constraint title_copy_foreign foreign key(t_id) references title(id),
constraint title_copy_status check(status in('已借出','未借出') )
);
--方法2:
create table title_copy(
id number(3) not null,
t_id number(3) not null,
status char(9) not null,
constraint title_copy_primary primary key(id),
constraint title_copy_foreign foreign key(t_id) references title(id)
);
alter table title_copy modify status default '未借出' constraint title_copy_status check(status in ('已借出','未借出'));