Variable uses and placement

Question

I'm new to PL/SQL and am trying to learn about variable valid uses/placement (any pointers to any docs is appreciated...)
All of the docs I've looked only mention declaration and assignment not valid placement.
When I use an input parameter to a cursor placement matters . I just don't understand why...
example... using the value "SCOTT" as an input parm to the c10 cursor replaces the "str_in" variable correctly and works...
1 declare
2 cursor c10(str_in IN varchar2) is
3 select username
4 from dba_users where username=str_in ;
5 begin
6 for r_c10 in c10('SCOTT') loop
7 dbms_output.put_line(r_c10.username);
8 end loop;
9* end;
SQL> /
SCOTT
PL/SQL procedure successfully completed.
However, when trying to replace another "word" it won't resolve the reference...
example... attempting to replace the from table_name as an input parm, no go...
1 declare
2 cursor c10(str_in IN varchar2) is
3 select username
4 from str_in where username='SCOTT' ;
5 begin
6 for r_c10 in c10('DBA_USERS') loop
7 dbms_output.put_line(r_c10.username);
8 end loop;
9* end;
SQL> /
from str_in where username='SCOTT' ;
ERROR at line 4:
ORA-06550: line 4, column 6:
PL/SQL: ORA-00942: table or view does not exist
ORA-06550: line 3, column 1:
PL/SQL: SQL Statement ignored
ORA-06550: line 7, column 26:
PLS-00364: loop index variable 'R_C10' use is invalid
ORA-06550: line 7, column 5:
PL/SQL: Statement ignored
Why can't it resolve the string ?
Any help is appreciated
dumb newbie...

Answer 1

Hi Jeff,
Welcome to the forum !
The query that is executed is always the same irrespective of the input parameter as this is STATIC sql.
Only the variables can be input parameters.
If you want the table name to change based on the input, you need to use dynamic sql.
Can you explain what you are trying to do with this program?
Thanks,
Rajesh.
--you can include the code in before and after the statement to preserve spaces.
Edited by: Rajesh Chamarthi on Oct 22, 2009 11:02 AM