What could be the problem?

What are the symptoms? Does your code behave is some way other than you intended? If so what way?

my $query_records2 = $conn->prepare($mainquery) or die("Error on prepa
+ring the sql statement2 \n");
$query_records2->execute() or die("Error on getting the data from QUER
+YDETAIL \n");
[download]

Consider including the actual error ($DBI::errstr or the errstr() method) in your error messages. If you code is failing it can make much easy to figure out why.