Assign dynamic statement in declare block or begin block

Question

Hi all,
For below code, if I assign the select statement in the declare section for corresponding variable, will it improve the performance.
For cust_veh_id we have another cursor in declare block, only partial code is provided.
What I meant.
declare
v_addr_chg_stmt                 varchar2(2000) := 'select ''Y''
FROM cust_addrs addrs
WHERE customer_id = :v_customer_id
AND updated_date >:p_end_date
and rownum = 1';Actaul
declare
p_end_date                      date;
v_addr_chg_stmt                 varchar2(2000);
v_mileage_stmt                 varchar2(2000);
begin
select updated_date into p_end_date
from process_log_rfsh
where tran_code ='CAP';
v_addr_chg_stmt :=
'select ''Y''
FROM cust_addrs addrs
WHERE customer_id = :v_customer_id
AND updated_date >:p_end_date
and rownum = 1'
v_mileage_stmt :=
'SELECT ''Y'' FROM cust_vehicles_audit
WHERE cust_veh_id=:v_cust_veh_id
AND field_name =''LAST_MILEAGE''
AND added_date > :p_end_date
and audit_date >= trunc(:p_end_date)
and rownum=1'
       begin
                 execute immediate v_addr_chg_stmt
                    into v_addr_change_flag
                    using v_customer_id,  p_end_date;
             exception
          when no_data_found then
                 v_addr_change_flag:='N';
             end;
        begin
               execute immediate v_mileage_stmt
                 into v_mileage_change_flag
                using v_cust_veh_id,  p_end_date, p_end_date;
           exception
         when no_data_found then
               v_mileage_change_flag:='N';
           end;
end;Thanks
Raghu
Edited by: Raghu on 18 Jan, 2013 1:13 PM

Answer 1

Raghu wrote:
This code is already running in production from few years.Not a valid reason to justify using dynamic SQL.
YOU NEED JUSTIFICATION FOR USING DYNAMIC CODE. In any language.
Again: WHAT is your justification? If you cannot provide that, then why are you using dynamic code??
If we have to use dynamic sql, performance wise defining in declare block or begin will be better.No difference - as neither method changes the actual SQL cursor executed. Neither makes the resulting cursor read data blocks faster.
PL/SQL also does not care where variable assignment happens. The difference is so tiny and so small, it is irrelevant to performance:
SQL> declare
  2          t1      timestamp;
  3  begin
  4          --// test 1
  5          t1 := systimestamp;
  6          for i in 1..10000 loop
  7                  declare
  8                          num     number;
  9                  begin
10                          num := 1;
11                  end;
12          end loop;
13          dbms_output.put_line( 'Test 1. '||to_char(systimestamp-t1) );
14 
15          --// test 2
16          t1 := systimestamp;
17          for i in 1..10000 loop
18                  declare
19                          num     number := 1;
20                  begin
21                          null;
22                  end;
23          end loop;
24          dbms_output.put_line( 'Test 2. '||to_char(systimestamp-t1) );
25 
26  end;
27  /
Test 1. +000000000 00:00:00.000040000
Test 2. +000000000 00:00:00.000024000
PL/SQL procedure successfully completed.
SQL>