Calling a function from an explicit cursor - sql

Question

I need to call the stored function findtotalcarmodels from this PL/SQL block. The way this code is written is not the way I would do it in production, however it is an exercise in 'lateral' thinking.
SET SERVEROUTPUT ON FORMAT WRAP SIZE 12000
Declare
v_model VARCHAR2(40);
v_cost NUMBER;
v_reg VARCHAR2(10);
v_carcategory VARCHAR2(40);
v_totalcars NUMBER;
v_count DATE;
v_maxcount DATE;
v_maxdept VARCHAR2(20);
cursor carcur IS
SELECT * FROM i_car;
v_car carcur%ROWTYPE;
Cursor c_date (p_reg i_booking.registration%TYPE) IS
SELECT date_reserved
FROM i_booking
WHERE registration = p_reg;
v_date c_date%ROWTYPE;
Begin
v_totalcars := findtotalcarmodels();
FOR v_car IN carcur LOOP
If v_cost <=50000 THEN v_carcategory := 'Budget Car';
End IF;
If v_cost BETWEEN 50000 AND 100000 THEN v_carcategory := 'Standard Car';
End IF;
If v_cost >100000 THEN v_carcategory := 'Premium Car';
End If;
FOR v_date IN c_date(v_car.registration) LOOP
v_count := v_count + 1;
END LOOP;
IF v_count > v_maxcount THEN
v_maxcount := v_count;
v_maxdept := v_car.registration;
END IF;
DBMS_OUTPUT.PUT_LINE('Registration:'|| ' '|| v_car.registration);
DBMS_OUTPUT.PUT_LINE('Cost:'|| '$' ||v_car.Cost);
DBMS_OUTPUT.PUT_LINE('Model Name:'|| ' '||v_car.model_name);
DBMS_OUTPUT.PUT_LINE('Car Category:'|| ' '||v_carcategory);
DBMS_OUTPUT.PUT_LINE('Total number of Cars:'|| ' '||v_totalcars);
DBMS_OUTPUT.PUT_LINE('Most Recent Rental Date: '|| ' '||v_maxcount);
DBMS_OUTPUT.NEW_LINE;
END LOOP;
END;
I am getting the error:
v_totalcars := findtotalcarmodels();
*
ERROR at line 19:
ORA-06550: line 19, column 16:
PLS-00306: wrong number or types of arguments in call to 'FINDTOTALCARMODELS'
ORA-06550: line 19, column 1:
PL/SQL: Statement ignored
Am I calling my function correctly in the right position?
This is the function:
CREATE OR REPLACE Function findtotalcarmodels
(model_name_in IN varchar2)
RETURN NUMBER
IS
counter INTEGER := 0;
CURSOR car_count_cur IS
SELECT model_name FROM i_car WHERE model_name = model_name_in;
Rec_car_details car_count_cur%ROWTYPE;
BEGIN
OPEN car_count_cur;
LOOP
FETCH car_count_cur INTO Rec_car_details;
EXIT WHEN car_count_cur%NOTFOUND;
counter := counter + 1;
END LOOP;
CLOSE car_count_cur;
RETURN counter;
END;

Answer 1

Okay, so I have no idea why you're getting that error with that function. The error indicates that you're not giving the function the correct number of arguments. Judging by the function that's clearly not what's happening, or it's not the same function.
You've just changed the function call; the function requires an argument so the "incorrect" code you had in your first revision was actually correct.
However, let's put that to one side for a second and look again at what you're doing.
Your function is a count on a table. There's no need for a cursor or looping, incrementing variables or anything. You can simplify it to
select count(*) from i_car where model_name = :model_name
You never assign the variables v_count or v_maxcount a value so incrementing them will still result in a NULL. They're dates anyway, so it's a little strange to be incrementing them.
Your cursor c_date is just another count; once again no need for a loop.
The model_name variable is never initialised so your function will not return a result.
There are a lot of ways to simplify this; though I'm going to guess a few things here. Change your carcur cursor to the following:
select i.*
, case cost
when <= 50000 then 'Budget Car'
when <= 100000 then 'Standard Car'
else 'Premium Car'
end as category
, count(*) over ( partition by model_name ) as total_cars
from i_cars
This appears to enable you to remove your IF statements and your function. You can then remove your second loop by performing an outer join on i_booking (you need to add the primary key in yourself):
select i.*
, case c.cost
when <= 50000 then 'Budget Car'
when <= 100000 then 'Standard Car'
else 'Premium Car'
end as category
, count(distinct c.primary_key)
over ( partition by c.model_name ) as total_cars
, count(b.date_reserved)
over ( partition by b.registration ) as reserved_ct
from i_cars c
left outer join i_booking b
on c.registration = b.registration
I'm not 100% certain on the max stuff as it's not clear at all where it's assigned (it's not) but it looks as though you might be wanting to find the maximum count by model etc, in which case you can use a sub-query on the above cursor:
select sub.*
, max(total_cars) over () as max_cars
, max(reserved_ct) over () as max_reserved
from ( select i.*
, case c.cost
when <= 50000 then 'Budget Car'
when <= 100000 then 'Standard Car'
else 'Premium Car'
end as category
, count(distinct c.primary_key)
over ( partition by c.model_name ) as total_cars
, count(b.date_reserved)
over ( partition by b.registration ) as reserved_ct
from i_cars c
left outer join i_booking b
on c.registration = b.registration
) sub
If you then need to output it (there's rarely a need) you can loop through this single SQL statement, which gives you everything in one go:
declare
c_cursor is
select sub.*
, max(total_cars) over () as max_cars
, max(reserved_ct) over () as max_reserved
from ( select i.*
, case c.cost
when <= 50000 then 'Budget Car'
when <= 100000 then 'Standard Car'
else 'Premium Car'
end as category
, count(distinct c.primary_key)
over ( partition by c.model_name ) as total_cars
, count(b.date_reserved)
over ( partition by b.registration ) as reserved_ct
from i_cars c
left outer join i_booking b
on c.registration = b.registration
) sub
;
begin
for i in c_cursor loop
dbms_output.put_line(i.registration);
dbms_output.put_line(i.cost);
...
end loop;
end;
I've reduced a PL/SQL block and a function to a single SQL statement; it may not be spot on because there's so many unknowns but it's worth trying for yourself. Simple is almost always better.