Hi MS,
I done small changes try this ,
select T1. Dscription,T1.docEntry,T1.Quantity,T1.Price , isnull(T2.LineText,'') from OQUT T0 INNER JOIN QUT1 T1 ON T0.DocEntry = T1.DocEntry left JOIN QUT10 T2 ON T1.DocEntry = T2.DocEntry and t1.linenum=t2.aftlinenum where T1.DocEntry='590'
-Rajesh NS