Basic anonymous block which drops and creates a table

Question

Version: 11.2.0.3
I am fairly new to PL/SQL.
We have a table named CHK_CNFG_DTL.
I want to create a backup table for CHK_CNFG_DTL which will be named like CHK_CNFG_DTL_BKP_<timestamp> eg: CHK_CNFG_DTL_BKP_JULY_22_2013
Creation of this backup table has to be automated so, I want to create an anonymous block which will first drop the existing backup table and then create a new backup table from the original table.
The below code works fine. But the very first time when you run it , the loop won't iterate because there is no such table named CHK_CNFG_DTL_BKP%.
declare
v_stmt varchar2(1000);
v_date date;
begin
  for rec in
  (select * from user_tables where table_name like 'CHK_CNFG_DTL_BKP%' )
    loop
        begin
            execute immediate 'alter session set nls_date_format=''DD_MON_YYYY''';
            v_stmt := 'drop table '||rec.table_name|| ' purge';
            dbms_output.put_line(v_stmt);   ----- Drops Old backup table
            execute immediate v_stmt;
            select sysdate into v_date from dual;
            v_stmt := 'create table CHK_CNFG_DTL_BKP_'||to_date(v_date)||' as select * from CHK_CNFG_DTL';
            dbms_output.put_line('Creating Bkp table CHK_CNFG_DTL_BKP_'|| to_date(v_date) );
            dbms_output.put_line(v_stmt);
            execute immediate v_stmt;  --- Creates new Backup table
        exception
        when others
        then
        dbms_output.PUT_LINE (rec.table_name||'-'||sqlerrm);
        end;
    end loop;
end;
PL/SQL procedure successfully completed.
-- Backup table not created.
SQL> select table_name from user_Tables where table_name like 'CHK_CNFG_DTL%';
TABLE_NAME
CHK_CNFG_DTL
Of course, this can fixed by creating a table like bleow before executing the anonymous block
SQL> create table CHK_CNFG_DTL_BKP_JULY_22_2013 (x varchar2(37));
Table created.
and now the block will succesfully run like
24  end;
25  /
drop table CHK_CNFG_DTL_BKP_JULY_22_2013 purge
Creating Bkp table CHK_CNFG_DTL_BKP_22_JUL_2013
create table CHK_CNFG_DTL_BKP_22_JUL_2013 as select * from CHK_CNFG_DTL
PL/SQL procedure successfully completed.
But this is going to production . We can't a table like CHK_CNFG_DTL_BKP_JULY_22_2013 without a proper business reason.
How can I modify the above code so that if even if there is no such table like 'CHK_CNFG_DTL_BKP%' , it will proceed to create the backup table?

Answer 1

Hi,
Why won't you push the creation of the backup out of the loop ?
declare
v_stmt varchar2(1000);
v_date date;
begin
  for rec in
  (select * from user_tables where table_name like 'CHK_CNFG_DTL_BKP%' )
    loop
        begin
            execute immediate 'alter session set nls_date_format=''DD_MON_YYYY''';
            v_stmt := 'drop table '||rec.table_name|| ' purge';
            dbms_output.put_line(v_stmt);   ----- Drops Old backup table
            execute immediate v_stmt;
        exception
        when others
        then
        dbms_output.PUT_LINE (rec.table_name||'-'||sqlerrm);
        end;
    end loop;
            select sysdate into v_date from dual;
            v_stmt := 'create table CHK_CNFG_DTL_BKP_'||to_date(v_date)||' as select * from CHK_CNFG_DTL';
            dbms_output.put_line('Creating Bkp table CHK_CNFG_DTL_BKP_'|| to_date(v_date) );
            dbms_output.put_line(v_stmt);
            execute immediate v_stmt;  --- Creates new Backup table
end;