Need SQL Server query to aggregate data for multiple rows

Question

I have a table with customer information that I need to aggregate the data for into one row. My unique identifier is my customer number. How can i achieve that? Here is my current data:

        ID  CUST_NUM    CUSTOMER_NAME                       BOUGHT_PRODUCT_A    BOUGHT_PRODUCT_B  BOUGHT_PRODUCT_C  BOUGHT_PRODUCT_D
        1   125654      IHOP                                NULL                NULL              NULL              YES
        2   125654      I.H.O.P.                            YES                 NULL              NO                YES
        3   125654      IHOP INC.                           YES                 NULL              NULL              NULL

And this is my desired outcome:

        ID  CUST_NUM    CUSTOMER_NAME          BOUGHT_PRODUCT_A    BOUGHT_PRODUCT_B  BOUGHT_PRODUCT_C   BOUGHT_PRODUCT_D
        1   125654      IHOP,I.H.O.P.,IHOP INC. NULL                NULL              NULL              YES

Answer 1

You can use window function:

select distinct CUST_NUM,
       stuff ((select distinct ',' +CUSTOMER_NAME  
               from table 
               where t.CUST_NUM = CUST_NUM for xml path('')
               ), 1,1, ''
             ) as CUSTOMER_NAME, 
       first_value(BOUGHT_PRODUCT_A) over (partition by CUST_NUM order by ID) BOUGHT_PRODUCT_A,
       first_value(BOUGHT_PRODUCT_B) over (partition by CUST_NUM order by ID) BOUGHT_PRODUCT_B,
       first_value(BOUGHT_PRODUCT_C) over (partition by CUST_NUM order by ID) BOUGHT_PRODUCT_C,
       first_value(BOUGHT_PRODUCT_D) over (partition by CUST_NUM order by ID) BOUGHT_PRODUCT_D
from table t;