Bind variable vs. variable....

Question

Hi ,
In the Oracle Master Glossary ... there is the following explanation about bind variable:
A variable in a SQL statement that must be replaced
with a valid value, or the address of a value, in order
for the statement to successfully execute
According to the above .. which is the difference between bind variable and variable....????
Tom Kyte in one , at least, of his book... points out to use the bind variables...not simple variables.
He also proves this using the following example:
tkyte@TKYTE816> set timing on
tkyte@TKYTE816> declare
2 type rc is ref cursor;
3 l_rc rc;
4 l_dummy all_objects.object_name%type;
5 l_start number default dbms_utility.get_time;
6 begin
7 for i in 1 .. 1000
8 loop
9 open l_rc for
10 ʹselect object_name
11 from all_objects
12 where object_id = ʹ || i;
13 fetch l_rc into l_dummy;
14 close l_rc;
15 end loop;
16 dbms_output.put_line
17 ( round( (dbms_utility.get_time‐l_start)/100, 2 ) ||
18 ʹ seconds...ʹ );
19 end;
20 /
14.86 seconds...[[/b]pre]
And using bind variables
tkyte@TKYTE816> declare
2 type rc is ref cursor;
3 l_rc rc;
4 l_dummy all_objects.object_name%type;
5 l_start number default dbms_utility.get_time;
6 begin
7 for i in 1 .. 1000
8 loop
9 open l_rc for
10 ʹselect object_name
11 from all_objects
12 where object_id = :xʹ
13 using i;
14 fetch l_rc into l_dummy;
15 close l_rc;
16 end loop;
17 dbms_output.put_line
18 ( round( (dbms_utility.get_time‐l_start)/100, 2 ) ||
19 ʹ seconds...ʹ );
20 end;
21 /
1.27 seconds...I'm confused as in my PL/SQL programs i do not use of course literal values but 'simple variables' not 'bind variables'....
Should i replace all uses and occurences of 'simple variables' with bind variables...?????
Thanks....a lot
Sim

Answer 1

No need for something as complex as SQL tracing. Simply look in the shared pool. E.g.
SQL> create or replace procedure foo2 is
2 n number := 1;
3 c number;
4 begin
5 select
6 count(*) into c
7 from dept
8 where deptno = n;
9 end;
10 /
Procedure created.
SQL> -- we flush the shared pool and remove cached cursors
SQL> alter system flush shared_pool;
System altered.
SQL> -- is there a cursor in the shared pool using DEPT as our stored proc is using?
SQL> select
2 sql_text
3 from v$sqlarea
4 where sql_text like UPPER('%dept%')
5 and sql_text not like '%v$sqlarea%';
no rows selected
SQL> -- we execute our stored proc which will cause our SQL in that stored proc to be cached
SQL> exec Foo2
PL/SQL procedure successfully completed.
SQL> -- do we see our stored proc's SQL in the shared pool using a bind variable?
SQL> select
2 sql_text
3 from v$sqlarea
4 where sql_text like UPPER('%dept%')
5 and sql_text not like '%v$sqlarea%';
SQL_TEXT
SELECT COUNT(*) FROM DEPT WHERE DEPTNO = :B1
SQL>