MySQL join on 2 tables - mysql

Question

I need to do a search on 2 simultaneous tables, and I thought that this join would work but its giving me an incorrect syntax error.
$return_arr = array();
$query = mysql_query("SELECT * FROM clients WHERE lastname LIKE '$q%' AND agencyid = '$agencyid'
UNION
SELECT * FROM busclients WHERE busname LIKE '$q%' AND agencyid = '$agencyid'")or die(mysql_error());
if($query) {
while ($result = mysql_fetch_array($query)) {
if(isset($result['busname'])){
$description['id'] = $result['ID'];
$description['value'] = $result['busname'] ;
array_push($return_arr,$description);
}
else
{
$description['id'] = $result['ID'];
$description['value'] = $result['lastname'] . ", " . $result['firstname'] ;
array_push($return_arr,$description);
}
}
}
echo json_encode($return_arr);
Edited with fix suggested below and entire syntax
This is a query from an autocomplete search box. So when someone types in a client or business client name, it uses this query to search the database and then displays the results using jquery.
The fix below works but when I do a search on a business client it is returning []. A client search works fine.

Answer 1

You could use two seperate query's and join them together like so:
SELECT * FROM clients
WHERE lastname LIKE "%agencyid%"
UNION
SELECT * FROM busclients
WHERE busname LIKE "%$agencyid%";

Answer 2

You sql syntax shoul look like this :
SELECT * FROM clients c
inner join
busclients b
on c.agencyid=b.idbus
WHERE (c.lastname and b.busname LIKE '$q%') AND c.agencyid = '$agencyid'
Just to complete the circle make sure you read this article on how to join tables in mysql