Join two tables with additional field in one table [duplicate] - sql

Question

This question already has answers here:
SQL JOIN and different types of JOINs
(6 answers)
Closed 3 years ago.
I would like to join together two tables with additional columns.
First table is for number of products despatched by product
** Table 1 - Despatches **
Month ProductID No_despatched
Jan abc 10
Jan def 15
Jan xyz 12
The second table is for the number of products returned by product, but also an additional column by return reason
** Table 2 - Returns **
Month ProductID No_returned Return_reason
Jan abc 2 Too big
Jan abc 3 Too small
Jan xyz 1 Wrong colour
I would like to join the tables to show returns and despatched on the same row with the number of despatched being duplicated if there are multiple return reasons for the same product.
** Desired output **
Month ProductID No_despatched No_returned Return_reason
Jan abc 10 2 Too big
Jan abc 10 3 Too small
Jan xyz 12 1 Wrong colour
Hope this makes sense...
Thanks in advance!
afk

Answer 1

This seems like a basic JOIN:
select r.month, r.productid, d.no_despathed, r.no_returned, r.return_reason
from returns r join
despatches d
on r.month = d.month and r.productid = d.productid;
The results don't seem particularly useful, because some products are missing (those with no returns). And the amounts are duplicated if there is more than one return record.

Answer 2

just use join
select a.*,b.No_returned,.Return_reason from
table1 join table2 on a.ProductID=b.ProductID
and a.month=b.month
In case of duplicate you may use distinct

Answer 3

Changing the order of clauses in your question produces the result.
with additional columns.
SELECT Table1.Month, Table1.ProductID, Table1.NoDespatched, Table2.NoReturned, Table2.ReturnReason
join two tables
FROM Table1 LEFT JOIN Table2
ON Table1.Month=Table2.Month AND Table1.ProductID=Table2.ProductID
We use a LEFT JOIN because, presumably a product can be dispatched without being returned, but nobody can return a product you didn't send out.