Basic question about PL/SQL SELECT statement, how to declare - sql

Question

I am trying to execute the function, but :
5/5 PLS-00103: begin function pragma procedure subtype type
current
cursor delete.
How can I repair it ?
create or replace function is_valid_value(resourceToCheck in varchar2,columnToCheck in varchar2,valueToCheck in varchar2)
return varchar2 is
v_value valid_values.resourceName%type;
declare
v_resource resourceToCheck;
v_name columnToCheck;
v_value valueToCheck ;
begin
begin
Select resourceName,columnName,validValue into v_resource,v_name,v_value
from valid_values
where
resourceName =resourceToCheck
AND columnName = columnToCheck
AND validvalue = valueToCheck
AND
upper(resourceName) = upper (valuetoCheck);
exception
when no_data_found then
return 0;
end;
return 1;
end is_valid_value ;

Answer 1

It seems you have several syntax errors in the routine:
-- function with 3 parameters
create or replace function is_valid_value(resourceToCheck in varchar2,
columnToCheck in varchar2,
valueToCheck in varchar2)
-- returns varchar2
return varchar2
is
-- uses 3 local variables; please, note their types
v_resource valid_values.resourceName%type;
v_name valid_values.columnName%type;
v_value valid_values.validValue%type;
begin
-- if we have a single record
select resourceName,
columnName,
validValue
into v_resource,
v_name,
v_value
from valid_values
where resourceName = resourceToCheck
and columnName = columnToCheck
and validvalue = valueToCheck
and upper(resourceName) = upper(valuetoCheck);
-- we return '1' (please, remember the declaration "return varchar2")
return '1';
exception
-- When we have no records
when no_data_found then
-- we return '0' (again, we return VarChar2)
return '0';
end is_valid_value;

Answer 2

You don't actually need the query to retrieve values just to indicate if there is a record or not. The following query seems to satisfy the requirement and be much simpler.
This way you avoid an EXCEPTION handler; neither return value is actually an exception so this seems more 'correct'.
I would also suggest using Y/N as the return if you want a VARCHAR2. Use 1/0 if you want to use a NUMBER. Mixing them could be confusing later for maintenance.
CREATE OR REPLACE FUNCTION is_valid_value(resourcetocheck IN VARCHAR2
, columntocheck IN VARCHAR2
, valuetocheck IN VARCHAR2)
RETURN VARCHAR2
IS
func_result VARCHAR2(1);
BEGIN
-- Indicate if it is a valid result
SELECT rec_exist
INTO func_result
FROM (SELECT '1' as rec_exist
FROM valid_values
WHERE resourcename = resourcetocheck
AND columnname = columntocheck
AND validvalue = valuetocheck
AND UPPER(resourcename) = UPPER(valuetocheck)
UNION ALL
SELECT '0' FROM dual)
WHERE rec_exist = 'Y' OR rownum = 1;
-- we return '1' (please, remember - VarChar2)
RETURN func_result;
END is_valid_value;