Conversion failed when converting the nvarchar value '29449,29446,29450,29534' to data type int - sql

Question

I am create a stored procedure in SQL and I get the following error when I execute the query:
Conversion failed when converting the nvarchar value '11021,78542,12456,24521' to data type int.
Any idea why?
SELECT
A.Art_ID, A.Title
FROM
Art A
INNER JOIN
Iss I ON A.Iss_ID = I.Iss_ID
INNER JOIN
Sections S ON A.Section_ID = S.Section_ID
INNER JOIN
iPadSec IPS ON A.Sec_ID = IPS.Sec_ID
WHERE
A.Art_ID IN (SELECT CAST(Art_IDs AS int) /***error happens here***/
FROM Book_Art b
WHERE Sub_ID = 68)
AND I.Iss > dateadd(month, -13, getdate())
AND A.Active = 1
AND IPS.Active = 1
AND A.PDate <= getdate()
ORDER BY
PDate DESC, Art_ID DESC;

Answer 1

You cannot do what you want using in. First, it is a really bad idea to store ids in lists in strings. You should be using a junction table.
That said, sometimes this is necessary. You can rewrite this line of code as:
EXISTS (SELECT 1 /***error happens here***/
FROM Book_Art b
WHERE Sub_ID = 68 AND
',' + Art_IDs + ',' LIKE '%,' + cast(A.Art_ID as varchar(255)) + ',%'
)
However, the performance would generally be on the lousy side and there is little prospect of speeding this up without fixing the data structure. Use a junction table instead of a string to store lists.

Answer 2

Adding this line works for me.
declare #ids varchar(1000)
select #ids = art_ids from book_art where sub_id = #Sub_ID
EXECUTE ( 'SELECT A.Art_ID, A.Title'
+ ' FROM Art A'
+ ' INNER JOIN Iss I ON A.Iss_ID = I.Iss_ID'
+ ' INNER JOIN Sections S ON A.Section_ID = S.Section_ID'
+ ' INNER JOIN iPadSec IPS ON A.Sec_ID = IPS.Sec_ID'
+ ' WHERE A.Art_ID IN (' + #ids + ')'
+ ' AND I.Iss > dateadd(month, -13, getdate())'
+ ' AND A.Active = 1'
+ ' AND IPS.Active = 1'
+ ' AND A.PDate <= getdate()'
+ ' ORDER BY PDate DESC,'
+ ' Art_ID DESC;'
)
END
Thank you all for your help :)