plsql - How to use variables in Oracle PL/SQL Function -

i'm sorry upfront because question seems easy. have function:

create or replace function costs_mk (viewname in varchar2 , where_clause in varchar2)  return varchar2     v_costs varchar2 (500);  begin    select listagg(costs, ';' ) within group (order costs)   v_costs   (select distinct (costs)          viewname         where_clause);    return v_costs; end costs_mk; 

however error-message:

error(13,30): pl/sql: ora-00920: invalid relational operator

i can't compile it. if use exact values viewname , where_clause desired result.

what doing wrong?

/edit: line 13

from viewname 

/edit #2: guys. helped me lot. didn't thought dynamic sql in first step, refresher ;).

i suggest add exception block along execute immediate have created procedure can similary create function

create or replace procedure costs_pk(viewname in varchar2 , where_clause in varchar2 )    v_costs varchar2 (500); sql_stmnt varchar2(2000); begin sql_stmnt := 'select listagg(cost, '';'' ) within group (order cost) (select distinct (cost) ' || viewname || ' ' || where_clause || ' ) '; --sql_stmnt := 'select listagg(cost, '';'' ) within group (order cost) (select distinct (cost) cost_tab cost >=123 ) '; execute immediate sql_stmnt v_costs ; dbms_output.put_line ('query   works  -- ' || v_costs); exception when others   dbms_output.put_line ('input :' || viewname || ' ,  ' || where_clause ); dbms_output.put_line (sql_stmnt ); dbms_output.put_line ('error message : ' || sqlcode || ' ' || sqlerrm ); end;  begin costs_pk('cost_tab','cost >= 123'); end; 

note: code has been tested

output:

query   works  -- 123;456