eSQL multiple join but with conditions - sql

Question

I've 3 tables as under
MERCHANDISE
+-----------+-----------+---------------+
| MERCH_NUM | MERCH_DIV | MERCH_SUB_DIV |
+-----------+-----------+---------------+
| 1 | car | awd |
| 1 | car | awd |
| 2 | bike | 1kcc |
| 3 | cycle | hybrid |
| 3 | cycle | city |
| 4 | moped | fixie |
+-----------+-----------+---------------+
PRIORITY
+----------+-----------+---------+---------+------------+------------+---------------+
| CUST_NUM | SALES_NUM | DOC_NUM | BALANCE | PRIORITY_1 | PRIORITY_2 | PRIORITY_CODE |
+----------+-----------+---------+---------+------------+------------+---------------+
| 90 | 1000 | 10 | 23 | 1 | 6 | NO |
| 91 | 1001 | 20 | 32 | 3 | 7 | PRI |
| 92 | 1002 | 30 | 11 | 2 | 8 | LATE |
| 93 | 1003 | 40 | 22 | 5 | 9 | 1MON |
+----------+-----------+---------+---------+------------+------------+---------------+
ORDER
+----------+-----------+---------+---------+-----------+-----------+
| CUST_NUM | SALES_NUM | DOC_NUM | COUNTRY | MERCH_NUM | MERCH_DIV |
+----------+-----------+---------+---------+-----------+-----------+
| 90 | 1000 | 10 | INDIA | 1 | car |
| 91 | 1001 | 20 | CHINA | 2 | bike |
| 92 | 1002 | 30 | USA | 3 | cycle |
| 93 | 1003 | 40 | UK | 4 | moped |
+----------+-----------+---------+---------+-----------+-----------+
I want to join the left joined table from the last two tables with the first one such that the MERCH_SUB_DIV 'awd' appears only once for each unique combination of merch_num and merch_div
the code I came up with is as under, but I'm not sure how do I eliminate the duplicate row just for the awd
select
ROW#, MERCH.MERCH_NUMBER, ORDPRI.MERCH_NUMBER, ORDPRI.CUST_NUM,
BALANCE, SALES_NUM, ITEM_NUM, RANK, PRIORITY_1
from (
select
ROW_NUMBER() OVER(
PARTITION BY ORD.DOC_NUM, ORD.ITEM_NUM
ORDER BY ORD.DOC_NUM, ORD.ITEM_NUM ASC
) AS Row#,
ORD.CUST_NUM, PRI.CUST_NUM, ORD.MERCH_NUM, ORD.MERCH_DIV, PRI.BALANCE,
pri.DOC_NUM, pri.SALES_NUM, pri.PRIORITY_1, pri.PRIORITY_2
from ORDER as ORD
left join PRIORITY as PRI on ORD.DOC_NUM = PRI.DOC_NUM
and ORD.SALES_NUMBER = PRI.SALES_NUM
where country_name in ('USA', ‘INDIA’)
) as ORDPRI
left join MERCHANDISE as MERCH on ORDPRI.DIV = MERCH.DIV
and ORDPRI.MERCH_NUM = MERCH.MERCH_NUM

Answer 1

You have to use 'DISTINCT' keyword to get unique values, but if your 'Priority table' & 'Order table' contains different values for Same MERCH_NUM then the final result contains the repetation of the 'MERCH_NUM'.
SELECT DISTINCT M.MERCH_NUMBER, O.MERCH_NUMBER, O.CUST_NUM, BALANCE, SALES_NUM,ITEM_NUM,RANK,PRIORITY_1
FROM priority_table P
LEFT JOIN order_table O ON P.CUST_NUM = O.CUST_NUM AND P.SALES_NUM=O.SALES_NUM AND P.DOC_NUM = O.DOC_NUM
LEFT JOIN merchandise_table M ON M.MERCH_NUM = O.MERCH_NUM

Answer 2

A way around can be to add one new Row_Number() in the outermost query having Partition by MERCH_SUB_DIV + all the columns in the final list and then filter final results based on the New Row_Number() . Follows a pseudo code that might help:
select
-- All expected columns in final result except the newRow#
ROW#, MERCH_NUM, CUST_NUM,
BALANCE, SALES_NUM, PRIORITY_1
from (
select
ROW#,
-- the new row number includes all column you want to show in final result
row_number() over ( PARTITION BY MERCH.MERCH_SUB_DIV ,
MERCH.MERCH_NUM, ORDPRI.MERCH_NUM, ORDPRI.CUST_NUM,
BALANCE, SALES_NUM, PRIORITY_1
order by (select 1 )) as newRow# ,
MERCH.MERCH_NUM, ORDPRI.CUST_NUM,
BALANCE, SALES_NUM, PRIORITY_1
from (
-- main query goes here
select
ROW_NUMBER() OVER(
PARTITION BY ORD.DOC_NUM --, ORD.ITEM_NUM
ORDER BY ORD.DOC_NUM ASC --, ORD.ITEM_NUM
) AS Row#,
ORD.CUST_NUM, ORD.MERCH_NUM, ORD.MERCH_DIV as DIV, PRI.BALANCE,
pri.DOC_NUM, pri.SALES_NUM, pri.PRIORITY_1, pri.PRIORITY_2
from #ORDER as ORD
left join #PRIORITY as PRI on ORD.DOC_NUM = PRI.DOC_NUM
and ORD.SALES_NUMBER = PRI.SALES_NUM
where country_name in ('USA', 'INDIA')
) as ORDPRI
left join #MERCHANDISE as MERCH on ORDPRI.DIV = MERCH.DIV
and ORDPRI.MERCH_NUM = MERCH.MERCH_NUM
) as T
-- final filter to get distinct values
where newRow# = 1
Sample code here .. Hope this helps!!