create table T(L1 char(3),L2 varchar(100))
insert T select '001','AAA'+char(10)+'AB'+char(10)+'CD'
insert T select '002','BB'+char(10)+'DDD'
go

declare @sql varchar(8000)
set @sql = ''
select @sql = @sql + replace(L2,char(10),''' union select '''+L1+''', ''')
from (select l1,char(10)+ l2 as l2 from t) a

set @sql =  stuff(@sql,1,8,'')+''''
exec(@sql)
drop table t

/*

          
---- ---- 
001  AAA
001  AB
001  CD
002  BB
002  DDD

*/