Update 1 table-col using 2 table-col from other table - sql

Question

Is it possible to update 1 column/field of my table using 2 column/field from other table?
i tried this query :
UPDATE TEMP_Quantity
SET SS = (SELECT Qty1, Qty2 FROM Table_Quantity
WHERE Id = #IdHolder AND ProductId = 7)
WHERE Id = #IdHolder
And Sql said this error:
Only one expression can be specified in the select list when the subquery is not introduced with EXISTS.`
SS = NVarchar (Because it can accept number or string base on the column that i will select)
can someone tell me the right way to do this? tia :)

Answer 1

Uhm... to answer your question, you can CONCAT both qty's
UPDATE t1
SET SS = CONCAT(t2.Qty1, t2.Qty2)
FROM TEMP_Quantity t1
INNER JOIN Table_Quantity t2 on t2.Id = t1.Id
WHERE t1.Id = #IdHolder
AND t2.ProductId = 7
But this just feels wrong.

Answer 2

Try this :
UPDATE TEMP_Quantity
SET SS = (SELECT CAST(Qty1 AS VARCHAR(10)) + CAST(Qty2 AS VARCHAR(10))
FROM Table_Quantity
WHERE Id = #IdHolder AND ProductId = 7)
WHERE Id = #IdHolder

Answer 3

You may use and examine the below script. I hope, it is usefull for you.
declare #qty1 int
declare #qty2 int
if object_id('tempdb..#dbDestination') is not null
drop table #dbDestination
create table #dbDestination(
Id int,
ss nvarchar(50)
)
if object_id('tempdb..#dbSource') is not null
drop table #dbSource
create table #dbSource(
Id int,
ProductId int,
qty1 int,
qty2 int
)
insert into #dbDestination(Id,ss) values (1,null),(2,null)
insert into #dbSource(Id,ProductId,qty1,qty2) values(1,7,10,3), (2,null,8,2)
UPDATE #dbDestination
SET SS = (
SELECT CAST(qty1 as nvarchar(50))+ cast(qty2 as nvarchar(50))
FROM #dbSource
WHERE Id = 1 AND ProductId = 7
)
WHERE Id = 1
select * from #dbDestination