I'm creating a database for a hypothetical video rental store. All I need to do is a procedure that check the availabilty of a specific movie (obviously the movie can have several copies). So I have to check if there is a copy available for the rent, and take the number of the copy (because it'll affect other trigger later..). I already did everything with the cursors and it works very well actually, but I need (i.e. "must") to do it without using cursors but just using "pure sql" (i.e. queries).
I'll explain briefly the scheme of my DB:
The tables that this procedure is going to use are 3: 'Copia Film' (Movie Copy) , 'Include' (Includes) , 'Noleggio' (Rent).
Copia Film Table has this attributes:
- idCopia
- Genere (FK references to Film)
- Titolo (FK references to Film)
- dataUscita (FK references to Film)
Include Table:
- idNoleggio (FK references to Noleggio. Means idRent)
- idCopia (FK references to Copia film. Means idCopy)
Noleggio Table:
- idNoleggio (PK)
- dataNoleggio (dateOfRent)
- dataRestituzione (dateReturn)
- dateRestituito (dateReturned)
- CF (FK to Person)
- Prezzo (price)
Every movie can have more than one copy. Every copy can be available in two cases:
The query I've tried to do is the following and is not working at all:
SELECT COUNT(*)
FROM NOLEGGIO
WHERE dataNoleggio IS NOT NULL AND dataRestituito IS NOT NULL AND idNoleggio IN (
SELECT N.idNoleggio
FROM NOLEGGIO N JOIN INCLUDE I ON N.idNoleggio=I.idNoleggio
WHERE idCopia IN (
SELECT idCopia
FROM COPIA_FILM
WHERE titolo='Pulp Fiction')) -- Of course the title is just an example
Well, from the query above I can't figure if a copy of the movie selected is available or not AND I can't take the copy ID if a copy of the movie were available.
(If you want, I can paste the cursors lines that work properly)
------ USING THE 'WITH SOLUTION' ---- I modified a little bit your code to this
WITH film
as
(
SELECT idCopia,titolo
FROM COPIA_FILM
WHERE titolo = 'Pulp Fiction'
),
copy_info as
(
SELECT N.idNoleggio, N.dataNoleggio, N.dataRestituito, I.idCopia
FROM NOLEGGIO N JOIN INCLUDE I ON N.idNoleggio = I.idNoleggio
),
avl as
(
SELECT film.titolo, copy_info.idNoleggio, copy_info.dataNoleggio,
copy_film.dataRestituito,film.idCopia
FROM film LEFT OUTER JOIN copy_info
ON film.idCopia = copy_info.idCopia
)
SELECT COUNT(*),idCopia FROM avl
WHERE(dataRestituito IS NOT NULL OR idNoleggio IS NULL)
GROUP BY idCopia
As I said in the comment, this code works properly if I use it just in a query, but once I try to make a procedure from this, I got errors. The problem is the final SELECT:
SELECT COUNT(*), idCopia INTO CNT,COPYFILM
FROM avl
WHERE (dataRestituito IS NOT NULL OR idNoleggio IS NULL)
GROUP BY idCopia
The error is: ORA-01422: exact fetch returns more than requested number of rows ORA-06512: at "VIDEO.PR_AVAILABILITY", line 9.
So it seems the Into clause is wrong because obviously the query returns more rows. What can I do ? I need to take the Copy ID (even just the first one on the list of rows) without using cursors.
You can try this -
WITH film
as
(
SELECT idCopia, titolo
FROM COPIA_FILM
WHERE titolo='Pulp Fiction'
),
copy_info as
(
select N.idNoleggio, I.dataNoleggio , I.dataRestituito , I.idCopia
FROM NOLEGGIO N JOIN INCLUDE I ON N.idNoleggio=I.idNoleggio
),
avl as
(
select film.titolo, copy_info.idNoleggio, copy_info.dataNoleggio,
copy_info.dataRestituito
from film LEFT OUTER JOIN copy_info
ON film.idCopia = copy_info.idCopia
)
select * from avl
where (dataRestituito IS NOT NULL OR idNoleggio IS NULL);