[SOLVED] Query help

[ShaolinF]

Hi Guys,

 

I have the following query:

 

$txn_query = mysql_query("SELECT txn_id FROM purchase WHERE txn_id = $_POST['txn_id']");

 

Now, what I want to do is if txn_id is found in the DB then I want to output an error. How can I do this ?

[elpaisa]

$txn_query = mysql_query("SELECT txn_id FROM purchase WHERE txn_id = $_POST['txn_id']");

 

$row = mysql_num_rows($txn_query);

 

if($row)

{

echo' error';

}