Tampaknya Anda perlu menggunakan kunci komposit untuk tabel WRITERS Anda. Contoh(diuji dengan Oracle 12c dan 11g, dbfiddle di sini ):
-- 4 authors
create table author ( authorid primary key, fname, lname )
as
select 1, 'fname_1', 'lname_1' from dual union all
select 2, 'fname_2', 'lname_2' from dual union all
select 3, 'fname_3', 'lname_3' from dual union all
select 4, 'fname_4', 'lname_4' from dual ;
-- 7 books
create table books ( isbn primary key, title )
as
select '978-1449324451', 'title_1' from dual union all
select '978-1449324452', 'title_2' from dual union all
select '978-1449324453', 'title_3' from dual union all
select '978-1449324454', 'title_1_4' from dual union all
select '978-1449324455', 'title_2_4' from dual union all
select '978-1449324456', 'title_3_4' from dual union all
select '978-1449324457', 'title_4_4' from dual ;
-- suppose that 4 books are written by one and the same author
create table bookauthor( authorid, isbn )
as
select A.authorid, B.isbn
from author A
join books B on A.authorid = substr( B.title, length( B.title ), 1 ) ;
Tambahkan beberapa batasan ke tabel BOOKAUTHOR, dan periksa isinya:
-- authorid, isbn
alter table bookauthor
add (
constraint ba_fk1 foreign key( authorid ) references author( authorid )
, constraint ba_fk2 foreign key( isbn ) references books( isbn )
, constraint ba_pk primary key ( authorid, isbn )
) ;
SQL> select * from bookauthor;
AUTHORID ISBN
---------- --------------
1 978-1449324451
2 978-1449324452
3 978-1449324453
4 978-1449324454
4 978-1449324455
4 978-1449324456
4 978-1449324457
Kode DDL "Asli" (dengan sedikit modifikasi) -> INSERT gagal
create table writers (
authorid varchar2( 4 )
, lname varchar2( 10 )
, fname varchar2( 10 )
, isbn char( 14 )
, title varchar2( 30 ) constraint title_nn not null
, constraint wt_pk primary key ( authorid )
, constraint wt_fk foreign key( isbn ) references books( isbn )
);
INSERT INTO writers
SELECT authorid, fname, lname, isbn, title
FROM author
JOIN bookauthor USING(authorid)
JOIN books USING(isbn);
-- ORA-00001: unique constraint (...WT_PK) violated
-- author 4 with 4 books!
Kode DDL yang disarankan (dan pengujian):
create table writers2 (
authorid varchar2( 4 )
, lname varchar2( 10 )
, fname varchar2( 10 )
, isbn char( 14 )
, title varchar2( 30 ) constraint title_nn2 not null
, constraint wt_pk2 primary key ( authorid, isbn )
, constraint wt_fk2 foreign key( isbn ) references books( isbn )
);
INSERT INTO writers2
SELECT authorid, fname, lname, isbn, title
FROM author
JOIN bookauthor USING(authorid)
JOIN books USING(isbn);
-- 7 rows inserted.
MEMILIH dari WRITERS2:
SQL> select * from writers2 ;
AUTH LNAME FNAME ISBN TITLE
---- ---------- ---------- -------------- ------------------------------
1 fname_1 lname_1 978-1449324451 title_1
2 fname_2 lname_2 978-1449324452 title_2
3 fname_3 lname_3 978-1449324453 title_3
4 fname_4 lname_4 978-1449324454 title_1_4
4 fname_4 lname_4 978-1449324455 title_2_4
4 fname_4 lname_4 978-1449324456 title_3_4
4 fname_4 lname_4 978-1449324457 title_4_4
Namun, tidak yakin mengapa Anda memerlukan tabel WRITERS - karena Anda dapat menghasilkan datanya dengan menjalankan kueri.
