My function in where clause? help me please.

Question

hello friends, I need to call my function in where clause as dummy example below:
declare
name_ table1.name%type;
function return_id(id number) return number is
begin
return 1;
end return_id;
begin
select name into name_
from table1
where id = return_id(table1.id);
end;
raise exception: 'the function doesn't used in where clause'. why????

Answer 1

-- CREATING A FUNCTION AVAILABLE THROUGH A PACKAGE SPEC.
SQL> ed
Wrote file afiedt.buf
  1  create package mypackage is
  2    function myfunc(p_val NUMBER) RETURN NUMBER;
  3* end;
SQL> /
Package created.
SQL> ed
Wrote file afiedt.buf
  1  create or replace package body mypackage is
  2    function myfunc(p_val NUMBER) RETURN NUMBER IS
  3    begin
  4      RETURN (p_val*p_val)-1;
  5    end;
  6* end;
SQL> /
Package body created.
SQL> declare
  2    v_myval NUMBER := 2;
  3  begin
  4    select mypackage.myfunc(v_myval)
  5    into   v_myval
  6    from   dual;
  7    dbms_output.put_line(v_myval);
  8    select mypackage.myfunc(v_myval)
  9    into   v_myval
10    from   dual;
11    dbms_output.put_line(v_myval);
12  end;
13  /
3
8
PL/SQL procedure successfully completed.
-- CREATING A STANDALONE DATABASE FUNCTION.
SQL> create or replace function myfunc2(p_val number) return number is
  2  begin
  3    return (p_val*2)+1;
  4  end;
  5  /
Function created.
SQL> ed
Wrote file afiedt.buf
  1  declare
  2    v_myval NUMBER := 2;
  3  begin
  4    select myfunc2(v_myval)
  5    into    v_myval
  6    from dual;
  7    dbms_output.put_line(v_myval);
  8    select myfunc2(v_myval)
  9    into    v_myval
10    from dual;
11    dbms_output.put_line(v_myval);
12* end;
SQL> /
5
11
PL/SQL procedure successfully completed.
-- CREATING A LOCAL FUNCTION IN THE ANONYMOUS PL/SQL BLOCK
SQL> ed
Wrote file afiedt.buf
  1  declare
  2    v_myval NUMBER := 2;
  3    function myfunc3(p_val number) return number is
  4    begin
  5      return (p_val*p_val*p_val);
  6    end;
  7  begin
  8    select myfunc3(v_myval)
  9    into    v_myval
10    from dual;
11    dbms_output.put_line(v_myval);
12    select myfunc3(v_myval)
13    into    v_myval
14    from dual;
15    dbms_output.put_line(v_myval);
16* end;
SQL> /
  select myfunc3(v_myval)
ERROR at line 8:
ORA-06550: line 8, column 10:
PLS-00231: function 'MYFUNC3' may not be used in SQL
ORA-06550: line 8, column 10:
PL/SQL: ORA-00904: : invalid identifier
ORA-06550: line 8, column 3:
PL/SQL: SQL Statement ignored
ORA-06550: line 12, column 10:
PLS-00231: function 'MYFUNC3' may not be used in SQL
ORA-06550: line 12, column 10:
PL/SQL: ORA-00904: : invalid identifier
ORA-06550: line 12, column 3:
PL/SQL: SQL Statement ignored
SQL>As you can see (and as previously mentioned by someone else) the function has to be available to the SQL engine either via a datavbase package or as a database function. If you declare the function locally within the anonymous PL/SQL block then the function only exists in the scope of that PL/SQL block and thus when your SQL statement is sent to the SQL engine for execution, the SQL engine can't see it.
;)