Surrounding query with parenthesis cause error For XML - sql-server

Question

When trying to wrap query for further processing I get an error by just putting parenthesis around the query. See query below, if I simply remove the wrapping parenthesis, the query works. But when I use the parenthesis I get this error:
Incorrect syntax near the keyword 'for'
(
select '; ' + [NAME]
from (select a.[NAME] as 'NAME'
from [MS].[dbo].[A_POSITIONS] a
where a.ID = 208418
except
select top 1 b.[NAME]
from [MS].[dbo].[A_POSITIONS] b
where b.ID = 208418) as c
for XML PATH(''),TYPE
)
Anyone have an idea on why this is happening?
Thanks!

Answer 1

Adding the parenthesis alone around your query leads to an error, but if you type a SELECT before the opening parenthesis the code will run, meaning that you can use it for further processing:
if OBJECT_ID('A_POSITIONS') is not null
drop table [dbo].[A_POSITIONS]
create table [dbo].[A_POSITIONS]([ID] int,[Name] varchar(100))
insert into [dbo].[A_POSITIONS] values
(208418, 'one'),(208418, 'two'),(208418, 'three'),(208418, 'four'),(208418, 'five')
select
(
select '; ' + [NAME]
from (select a.[NAME] as 'NAME'
from [MS].[dbo].[A_POSITIONS] a
where a.ID = 208418
except
select top 1 b.[NAME]
from [MS].[dbo].[A_POSITIONS] b
where b.ID = 208418) as c
for XML PATH(''),TYPE
)
One last consideration: TOP keyword without an ORDER BY clause is non-deterministic.
From Microsoft Docs (more info here):
When TOP is used in conjunction with the ORDER BY clause, the result set is limited to the first N number of ordered rows; otherwise, it returns the first N number of rows in an undefined order
So you should really consider adding an ORDER BY to the second part of your query:
select '; ' + [NAME]
from (select a.[NAME] as 'NAME'
from [MS].[dbo].[A_POSITIONS] a
where a.ID = 208418
except
select top 1 b.[NAME]
from [MS].[dbo].[A_POSITIONS] b
where b.ID = 208418
--Add an ORDER BY clause here
) as c
for XML PATH(''),TYPE