I have a problem concerning an University assignment
in SQL. I am running PostgreSQL. Below part of the E/R diagram
in ASCII art.
( #VisaExploitation )
|
-------- //\\ --------
| | // \\ | |
| 1 |<------------// \\---------| copy |
| | \\ from// | |
-------- \\ // --------
| \\// |
| |
/\ (#copy )
/ISA\
------
| |
| |
---- ----
| | | |
| 2 | | 3 |
----- -----
1: Film
2: SpecialFilm
3: HistoricalFilm
2 and 3 inherits from film :
In SQL I have the following tables
CREATE TABLE film(
VisaExploitation INTEGER NOT NULL,
DureeTournage INTEGER NOT NULL,
Titre VARCHAR( 50 ),
PRIMARY KEY ( VisaExploitation ) );
CREATE TABLE filmHistorique(
NbCostume INTEGER
) INHERITS ( film );
create table filmDocumentaire(
) INHERITS ( film );
I have a weak entity:
CREATE TABLE copie(
NumCopie INTEGER NOT NULL,
VisaExploitation INTEGER NOT NULL,
PRIMARY KEY( VisaExploitation, NumCopie ),
FOREIGN KEY( VisaExploitation ) REFERENCES film ON DELETE CASCADE );
The problem is I have to be able to have the constraint on
both 2 and 3 and I can't figure how to implement this.
Thanking you in Advance,
Lionel
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