Oracle Stored Procedure 'Learnings' issue - sql

Question

I have been tasked (as part of an assignment) to write a stored procedure in Oracle PL/SQL. There are 3 requirements that have to be met.
There must be 2 parameters, 1 IN and 1 OUT.
I must use an implicit cursor and SQL function to calculate a count of the numbers of fields of the same type (in this case the type is car models, so how many cars of each model are there).
I must use another implicit cursor to display the description of the models.
To be honest, I am at a loss. So far for the stored proc I have:
CREATE OR REPLACE Procedure model_details_sp
(p_model IN VARCHAR2,
p_noofcars OUT NUMBER)
IS
BEGIN
SELECT COUNT(Model_Name) INTO p_noofcars
FROM i_car
GROUP BY Model_Name;
END;
I really have no idea where to go from here. Any advice or direction would be most appreciated.
Many thanks.
Hi guys I appreciate all the comments. I wasn't very clear with the end requirements. I want to be able to call this procedure via an anonymous block so that the user will enter a model type (&vairalbe) and the procedure will display how many of that model types are in the database.

Answer 1

When dealing with this type of problems, first think about the data you're trying to capture.
Dealing with implicit cursors in PL/SQL require 1-row, so you need to make sure you understand the data.
In this case, you pass in a variable that you don't use in any of your queries, so I suggest you re-evaluate.
I don't have a database at hand to run this, but you should be able to work this out and hopefully get you a bit closer. I put it in an anonymous block so that I can write it really quick.
DECLARE
PROCEDURE model_details_sp (p_model IN VARCHAR2, p_noofcars OUT NUMBER)
IS
p_description VARCHAR2 (200);
BEGIN
--2
SELECT COUNT (model_name)
INTO p_noofcars
FROM i_car
WHERE model_name = p_model;
DBMS_OUTPUT.put_line ('No of Cars for model: ' || p_noofcars);
--3
SELECT model_description
INTO p_description
FROM i_car --the table should be the car_model table so that only one record is returned
WHERE model_name = p_model;
DBMS_OUTPUT.put_line ('Model Desc' || p_description);
END model_details_sp;
BEGIN
dbms_output.put_line('');
END;
To #David Aldridge comment:
Try running this--the result should be a failure--as you cannont select multiple rows using the into CLAUS, unless you aggregate the data:
DECLARE
p_num NUMBER;
BEGIN
SELECT LEVEL INTO p_num FROM DUAL CONNECT BY LEVEL <= 10;
dbms_output.put(p_num);
END;
The error you should see is this:
Error report:
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 4
01422. 00000 - "exact fetch returns more than requested number of rows"
*Cause: The number specified in exact fetch is less than the rows returned.
*Action: Rewrite the query or change number of rows requested

Answer 2

From the description and subsequent comments, this is the solution I would provide:
DECLARE
PROCEDURE model_details_sp
(p_model IN VARCHAR2,
p_noofcars OUT NUMBER)
IS
BEGIN
SELECT COUNT(*)
INTO p_noofcars
FROM i_car
WHERE model_name = p_model;
END;
no_of_cars NUMBER := 0;
BEGIN
model_details_sp(:model_name, no_of_cars);
dbms_output.put_line('no of cars for ' || :model_name || ' = ' || no_of_cars);
END;
I've created the PROCEDURE in-line but you can just as easily extract this to the database by removing it from the declare section and executing it with CREATE OR REPLACE.
This example assumes use of an IDE that supports bind variable replacement (:model_name) on execute of the anonymous block. In TOAD, for example, the "user" will be prompted to provide a value for :model_name.