What is the best approach to process data on row by row basis ?

Question

Hi Gurus,
I need to code stored proc to process sales_orders into Invoices. I
think that I must do row by row operation, but if possible I don't want
to use cursor. The algorithm is below :
for all sales_orders with status = "open"
check for credit limit
if over credit limit -> insert row log_table; process next order
check for overdue
if there is overdue invoice -> insert row to log_table; process
next order
check all order_items for stock availability
if there is item that has not enough stock -> insert row to
log_table; process next order
if all check above are passed:
create Invoice (header + details)
end_for
What is the best approach to process data on row by row basis like
above ?
Thank you for your help,
xtanto

Answer 1

Processing data row by row is not the fastest method out there. You'll be sending much more SQL statements towards the database than needed. The advice is to use SQL, and if not possible or too complex, use PL/SQL with bulk processing.
In this case a SQL only solution is possible.
The example below is oversimplified, but it shows the idea:
SQL> create table sales_orders
  2  as
  3  select 1 no, 'O' status, 'Y' ind_over_credit_limit, 'N' ind_overdue, 'N' ind_stock_not_available from dual union all
  4  select 2, 'O', 'N', 'N', 'N' from dual union all
  5  select 3, 'O', 'N', 'Y', 'Y' from dual union all
  6  select 4, 'O', 'N', 'Y', 'N' from dual union all
  7  select 5, 'O', 'N', 'N', 'Y' from dual
  8  /
Tabel is aangemaakt.
SQL> create table log_table
  2  ( sales_order_no number
  3  , message        varchar2(100)
  4  )
  5  /
Tabel is aangemaakt.
SQL> create table invoices
  2  ( sales_order_no number
  3  )
  4  /
Tabel is aangemaakt.
SQL> select * from sales_orders
  2  /
        NO STATUS IND_OVER_CREDIT_LIMIT IND_OVERDUE IND_STOCK_NOT_AVAILABLE
         1 O      Y                     N           N
         2 O      N                     N           N
         3 O      N                     Y           Y
         4 O      N                     Y           N
         5 O      N                     N           Y
5 rijen zijn geselecteerd.
SQL> insert
  2    when ind_over_credit_limit = 'Y' then
  3         into log_table (sales_order_no,message) values (no,'Over credit limit')
  4    when ind_overdue = 'Y' and ind_over_credit_limit = 'N' then
  5         into log_table (sales_order_no,message) values (no,'Overdue')
  6    when ind_stock_not_available = 'Y' and ind_overdue = 'N' and ind_over_credit_limit = 'N' then
  7         into log_table (sales_order_no,message) values (no,'Stock not available')
  8    else
  9         into invoices (sales_order_no) values (no)
10  select * from sales_orders where status = 'O'
11  /
5 rijen zijn aangemaakt.
SQL> select * from invoices
  2  /
SALES_ORDER_NO
             2
1 rij is geselecteerd.
SQL> select * from log_table
  2  /
SALES_ORDER_NO MESSAGE
             1 Over credit limit
             3 Overdue
             4 Overdue
             5 Stock not available
4 rijen zijn geselecteerd.Hope this helps.
Regards,
Rob.