OPEN emp_refcur FOR {plsql variable} giving error - sql

Question

I am novice in plsql development.
I have a problem opening cursor on plsql variable (which has my dynamic SQL query). I am on ORACLE 12 i believe.
Details below:
emp_refcur SYS_REFCURSOR; -- Cursor declaration
component_sql:= 'select * from emp'; -- Base SQL
-- dynamic sql based on business logic
IF SOME_CONDITION THEN
filters:= ' where DEP IN (''ABC'',''DEF'')';
ELSE
filters:= ' where age>50';
component_sql:= component_sql||filters; -- appending filter to my base sql
OPEN emp_refcur FOR component_sql; -- opening the cursor
LOOP
FETCH emp_refcur INTO result;
EXIT WHEN emp_refcur%NOTFOUND;
dbms_output.put_line(result);
END LOOP;
CLOSE emp_refcur;
Compiling this procedure shown error at line 'OPEN emp_refcur FOR component_sql' and error are
Error(90,9): PL/SQL: Statement ignored
Error(90,29): PLS-00382: expression is of wrong type
I do not want to use bind values like
'OPEN emp_refcur FOR p_query_string USING p_deptno, p_sal;'
I have tried multiple approaches
OPEN emp_refcur FOR ''||component_sql||''; -- This approach is not causing compilation error, but running the procedure resulting
ORA-00900: invalid SQL statement
AND
OPEN emp_refcur FOR 'select * from emp'||filters; -- This is resulting the error
ORA-00900: invalid SQL statement
Not sure what i am missing here. Please help.
NOTE: Please ignore if there are any SQL query syntax errors. Because the SQL which i am printing after appending the filters is executing fine and getting results when i run separately.

Answer 1

I tried with your code and it has no issues. PLS-00382: expression is of wrong type --> This is a syntax error. It has nothing to do with bind variables. What is the declaration for result? I don't see in the snippet.
PLS-00382: expression is of wrong type
Cause: An expression has the wrong datatype for the context in which it was found.
Action: Change the datatype of the expression. You might want to use datatype conversion functions.
Declare
emp_refcur SYS_REFCURSOR;
filters varchar2(100);
component_sql varchar2(100);
result varchar2(20);
Begin
component_sql:= 'select 1 from dual'; -- Base SQL
-- dynamic sql based on business logic
IF 1=1 THEN
filters:= ' UNION ALL SELECT 2 from dual';
ELSE
filters:= ' where age>50';
End if;
component_sql:= component_sql||filters; -- appending filter to my base sql
OPEN emp_refcur FOR component_sql ; -- opening the cursor
LOOP
FETCH emp_refcur INTO result;
EXIT WHEN emp_refcur%NOTFOUND;
dbms_output.put_line(result);
END LOOP;
CLOSE emp_refcur;
END;