ऐसा लगता है कि आपको अपनी WRITERS तालिका के लिए एक समग्र कुंजी का उपयोग करने की आवश्यकता है। उदाहरण (Oracle 12c और 11g के साथ परीक्षण किया गया, dbfiddle यहां ):
-- 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 ) ;
BOOKAUTHOR तालिका में कुछ बाधाएं जोड़ें, और इसकी सामग्री जांचें:
-- 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
"मूल" डीडीएल कोड (मामूली संशोधनों के साथ) -> INSERT विफल रहता है
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!
सुझाया गया डीडीएल कोड (और परीक्षण):
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.
WRITERS2 से चयन:
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
सुनिश्चित नहीं है कि आपको WRITERS तालिका की आवश्यकता क्यों होगी, हालांकि - क्योंकि आप एक क्वेरी चलाकर इसका डेटा उत्पन्न कर सकते हैं।
