Complex Query Incorrect Syntax Error - sql

Question

I have tried to search for a solution to this but I have not been able to find one that fits this situation.
First I must say that my SQL is a lot rusty. The following query is the most complex one I have ever done to date.
Here is the query:
Declare #root varchar(Max)
set #root = ''
Select
ib.irrnum, ib.status, pu.probtype,
ib.submitby, ta.[Task Action], ib.area, co.cost,
rc.rootcause, ib.jobnum
From
tbl_irrbase ib
Left Join
tbl_cost co On ib.irrnum = co.irrnum
Left join
(Select Distinct probtype, irrnum
From tbl_probtype) pu On ib.irrnum = pu.irrnum
Left Join
(Select Distinct rootcause, irrnum
From tbl_rtcause) rc On ib.irrnum = rc.irrnum
Left Join
(Select TOP 1
(owner + Space(1) + Convert(varchar(10), senddate, 101) + Space(1) + taskitem) As 'Task Action',
irrnum
From
(select * From tbl_taskaction) ta
Order by
senddate Desc, sendtime Desc) ta On ib.irrnum = ta.irrnum
left Join
(Select [#root] = #root + rs.rootsource + Space(3), irrnum
From tbl_rtsource rs
Where rs.entrydate Between '10/04/2016' And '10/06/2016'
Select #root As 'Root Source') sr On ib.irrnum = sr.irrnum
Where
ib.submitedate between '09/28/2016' And '10/05/2016'
My problem is with the last Left Join line. If I take the entire Select statement out and run it in SSMS it runs fine, no errors. But when I try and run it in this query I get an error, red squiggly line under 'Select #root As' telling me the following:
Incorrect Syntax near 'Select'.
Expecting ')', EXCEPT, or UNION
I do not know how to fix this. If I remove this last 'Left Join' line the query runs fine.
Any ideas?

Answer 1

Instead of the last LEFT JOIN, try something like this:
CROSS APPLY (
SELECT (
SELECT rs.rootsource + Space(3)
From tbl_rtsource rs
Where rs.entrydate Between '10/04/2016' And '10/06/2016'
AND rs.irrnum=ib.irrnum
FOR XML PATH('')
) AS rootsource
) sr
Then include sr.rootsource in the columns of the first SELECT.