What kind of join should i use?

Question

Hi
I have the following mock example
WITH data AS(SELECT  99.99 retail_value, 6545 sales_value, 7 tran_type from dual union all
             SELECT  776.99 retail_value,774 sales_value,   8 tran_type from dual union all
             SELECT  929.99 retail_value, 56 sales_value, 8 tran_type from dual union all
             SELECT  44.99 retail_value, 35 sales_value,   8 tran_type from dual union all
             SELECT  776.99 retail_value,17 sales_value,   7 tran_type from dual union all
             SELECT  44.99 retail_value, 2 sales_value,   7 tran_type from dual),
     commercial_model AS(SELECT 1 com_id, 7 tran_type from dual union all
                         SELECT 1 com_id, 8 tran_type from dual union all
                         SELECT 2 com_id, 8 tran_type from dual union all
                         SELECT 2 com_id, 7 tran_type from dual)      
     SELECT * FROM data,commercial_model
     WHERE data.tran_type=commercial_model.tran_type
     AND com_id= /*input_parameter*/com_idNormally an input parameter is passed in to determine the com_id. However in the piece of work i'm having trouble with no com_id is being passed in so the sales report is picking both commercial_model transaction types and producing duplicate results. When i sum the sales_value field the figure is twice it should be.
Is there a way of joining the two tables so that i dont get these duplicates for tran_type.
Cheers in advance.

Answer 1

WITH data AS(SELECT  99.99 retail_value, 6545 sales_value, 7 tran_type from dual union all
             SELECT  776.99 retail_value,774 sales_value,   8 tran_type from dual union all
             SELECT  929.99 retail_value, 56 sales_value, 8 tran_type from dual union all
             SELECT  44.99 retail_value, 35 sales_value,   8 tran_type from dual union all
             SELECT  776.99 retail_value,17 sales_value,   7 tran_type from dual union all
             SELECT  44.99 retail_value, 2 sales_value,   7 tran_type from dual),
     commercial_model AS(SELECT 1 com_id, 7 tran_type from dual union all
                         SELECT 1 com_id, 8 tran_type from dual union all
                         SELECT 2 com_id, 8 tran_type from dual union all
                         SELECT 2 com_id, 7 tran_type from dual)      
     SELECT a.*, b.* FROM
          (select *  from data) a,
           (select distinct tran_type from  commercial_model
             where com_id = nvl( /*input parameter*/), com_id)
             ) b
     WHERE b.tran_type=a.tran_type