Dynamic Function- Oracle - oracle

Question

I am trying to create a function by giving 2 variables as inputs. These 2 variables are used dynamically in the function. Am using a select statement in the beginning of the loop to find the primary key column in a particular table. This column is assign to a variable value1. Am using this value1 variable as a sequence variable.
create FUNCTION Test(schemaname in varchar2, tablename in varchar2)
return number
IS cnpParmId NUMBER;
good VARCHAR(1) := 'F';
exist VARCHAR(1) := 'F';
value1 varchar2(500);
begin
good := 'F';
exist := 'F';
loop
SELECT cols.column_name into value1
FROM all_constraints cons, all_cons_columns cols
WHERE cols.TABLE_NAME= 'tablename'
And cols.OWNER='schemaname'
And cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner
ORDER BY cols.table_name, cols.position;
select schemaname.value1_seq.nextval into cnpParmId from dual;
begin
select 'T' into good from dual
where cnpParmId not in
(select value1 from schemaname.tablename);
exception when NO_DATA_FOUND then good := 'F';
end;
exit when good = 'T';
end loop;
return cnpParmId;
end;
/
Test(XYZ,ABC);
but am getting the following errors:
Error(21,11): PLS-00487: Invalid reference to variable 'SCHEMANAME'
Error(21,22): PL/SQL: ORA-02289: sequence does not exist
Error(23,7): PL/SQL: SQL Statement ignored
Error(25,38): PL/SQL: ORA-00942: table or view does not exist

Answer 1

When you introduce variables as table or column names you need to do a dynamic query using EXECUTE IMMEDIATE.
Your sequence query should be:
execute immediate 'select ' || schemaname || '.nextval from dual' into cnpParmId;
And your "get the return value" query should be:
execute immediate
'select ''T'' from dual where cnpParmId not in ' ||
'(select value1 from ' || schemaname || '.' || tablename || ')' into good;
Also note that your query to get value1 is looking for the literal values schemaname and tablename:
SELECT cols.column_name into value1
FROM all_constraints cons, all_cons_columns cols
WHERE cols.TABLE_NAME= 'tablename'
And cols.OWNER='schemaname'
... and so on
You can use variables to represent values, so just get rid of the single quotes around the variable names:
SELECT cols.column_name into value1
FROM all_constraints cons, all_cons_columns cols
WHERE cols.TABLE_NAME= tablename
And cols.OWNER=schemaname
... and so on