PHP MySQL上的多个表

I am trying to read table data and display in on a table the only thing is that i am trying to read it on 2 tables. The 2 tables have the same structure and i have tried it with the code below but nothing happens.

$sql = "SELECT pricedatamt5.symbol_name, pricedatamt5.symbol_bid, pricedatamt5.symbol_ask, pricedatamt4.symbol_bid, pricedatamt4.symbol_ask FROM pricedatamt5 LEFT JOIN pricedatamt4 ON pricedatamt5.symbol_name = pricedatamt4.symbol_name WHERE symbol_name='".$value."'";
            $result = mysql_query($sql);
            while($row = mysql_fetch_assoc($result))
            {
                echo "<tr>";
                echo "<td>".$row["symbol_date"]."</td>";
                echo "<td>".$row["symbol_bid"]."</td>";
                echo "<td>".$row["symbol_ask"]."</td>";
                echo "</tr>";
            }

I hope you can help me with this one because i am really having a hard time especially on retrieving data from 2 tables.

Thanks...

if you need the union your sql query will be:

$sql = "SELECT pricedatamt5.symbol_name, pricedatamt5.symbol_bid, pricedatamt5.symbol_ask FROM pricedatamt5 WHERE symbol_name='".$value."'"."
UNION
SELECT pricedatamt4.symbol_name, pricedatamt4.symbol_bid, pricedatamt4.symbol_ask  FROM pricedatamt4  WHERE symbol_name='".$value."'";

otherwise you should clarify your question.