I am looking to UNION two select statements, but have it so that the second select excludes some results if the first select contains certain records without using a temp table
I am trying to achieve something like this:
select customernumber, name into #tempCustomer1 from customers1
select customernumber, name from #tempCustomer1
UNION
select customernumber, name from customers2
where customernumber not in (select customernumber from #tempCustomer1)
order by customernumber
Is it possible to do this without a temp table?
It's a bit unclear what your desired end result is, but to answer your question Is it possible to do this without a temp table? Yes it is - you could do this:
select customernumber, name from customers1
UNION
(
select customernumber, name from customers2
where customernumber not in (select customernumber from customers1)
)
order by customernumber
This will return a set made up from the rows in customers1 and customers2 with the customer1 ids removed from customers2, I think this is what you want.
If you want to get rid of duplicate rows, this is done by the UNION
since you didn't add the ALL
option to it.
With this test setup:
declare @customers1 table (customernumber int, name char)
declare @customers2 table (customernumber int, name char)
insert @customers1 values (1,'a'),(2,'b')
insert @customers2 values (3,'d'),(4,'e'),(1,'f')
select customernumber, name from @customers1
UNION
(
select customernumber, name from @customers2
where customernumber not in (select customernumber from @customers1)
)
order by customernumber
The output would be:
customernumber name
1 a
2 b
3 d
4 e
Your query with UNION
should be doing exactly what you want cause Union discards the duplicate rows from the result set. So, you can just say
select customernumber, name from customers1
UNION
select customernumber, name from customers2
Per your comment, you can use a inline query to achieve the same without using temporary table like
SELECT * FROM
(
select customernumber, name from customers1
UNION
select customernumber, name from customers2
) tab
WHERE customernumber NOT IN (select customernumber from customers1)
ORDER BY customernumber
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