SQL - Updating rows in one table with values from another table - Multiple match - sql

Question

I am trying to append values in my Customer table with data from my Sales table.
The customer can have multiple records in the sales table:
Hereby a joined view:
SalesID CustomerID SalesComment CustomerComment
------------------------------------------------------------
1 14 Com1 Customer Comment 1
2 15 Com2 Customer Comment 2
3 14 Com3 Customer Comment 1
4 14 Customer Comment 1
I want to make an update like this:
UPDATE Customer
SET Customer.ShopBookKommentar = CAST([ShopBookKommentar] AS NVARCHAR(MAX)) +
CAST(CHAR(13) + CHAR(10) + S.Comments AS NVARCHAR(MAX))
FROM Customer C
INNER JOIN Sales S ON S.CustomerID = c.ID
But it's not updating any of the Customer rows where one of the Sales rows comment field is empty ('')

Answer 1

It looks like you are using SQL Server. You need to use the table alias for the update:
UPDATE c
SET ShopBookKommentar = c.ShopBookKommentar + CHAR(13) + CHAR(10) + S.Comments
FROM Costumer C INNER JOIN
Sales S
ON S.CostumerID = c.ID;
You only need the cast() if for some reason the intermediate result isn't big enough. But that shouldn't be a problem.
EDIT:
I am guessing that you actually want to apply multiple comments from different rows of Sales. That is a bit trickier:
UPDATE c
SET ShopBookKommentar = c.ShopBookKommentar + c.somm
FROM (SELECT c.*,
(SELECT CHAR(13) + CHAR(10) + S.Comments
FROM Sales s
WHERE S.CostumerID = c.ID AND
S.Comments IS NOT NULL
FOR XML PATH, TYPE
).value(N'.[1]', N'varchar(max)') as scomm
FROM c
) Costumer C INNER JOIN
(Sales S
ON ;