oracle 使用绑定变量极大的提升性能

SQL> alter system flush shared_pool;
SQL> set timing on;

declare
type rc is ref cursor;
l_rc rc;
l_dummy all_objects.object_name%type;
l_start number default dbms_utility.get_time;
begin
for i in 1..100
loop
open l_rc for
'select object_name from all_objects where object_id='||i;
fetch l_rc into l_dummy;
close l_rc;
end loop;
dbms_output.put_line(round((dbms_utility.get_time-l_start)/100,2)||'seconds...');
end;

执行结果：
PL/SQL procedure successfully completed
Executed in 14.196 secondsed

1 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..100
8           loop
9             open l_rc for
10             'select object_name from all_objects where object_id=:x'
11             using i;
12             fetch l_rc into l_dummy;
13             close l_rc;
14             end loop;
15             dbms_output.put_line(round((dbms_utility.get_time-l_start)/100,2)||'seconds...');
16 end;
17
18 执行结果：
19     PL/SQL procedure successfully completed
20     Executed in 0.141 seconds