How to display all the records from two mysql tables without displaying blank record?

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PHP

Tried google but no success. I am using php with mysql. I have two tables- pm and pm_reply. I want to display all the records from these tables. I am using left join to combine tables. Problem is if pm has a row and pm_reply is empty, i am getting all the records from pm along with blank record that is i think from pm_reply.

Now plz tell me how to display all the records from pm and pm_reply without this blank record.

Here is my pm table:

pm_id int not null primary key autoincrement,
subject varchar(50) not null,
message text not null

And Here is pm_reply table:

pm_reply_id int not null primary key autoincrement, 
pm_id int not null,
resubject varchar(50) not null,
details text not null

And here is my query:

$sql=mysql_query("select pm.*,  pm_reply.* FROM pm LEFT JOIN pm_reply ON pm.pm_id=pm_reply.pm_id" );