<?php
function eb_mine_views_query_alter(&$view, &$query) {
  if ($view->name == 'statuser') {
    dsm($query, 'before');
    $query->where[0]['type'] = 'OR';
    dsm($query, 'after');
  }
}
?>

SELECT node.title AS node_title, node.nid AS nid, node.created AS node_created
FROM
{node} node
INNER JOIN {taxonomy_index} taxonomy_index_value_0 ON node.nid = taxonomy_index_value_0.nid AND taxonomy_index_value_0.tid = :views_join_condition_0
INNER JOIN {taxonomy_index} taxonomy_index_value_1 ON node.nid = taxonomy_index_value_1.nid AND taxonomy_index_value_1.tid = :views_join_condition_1
WHERE ((( (taxonomy_index_value_0.tid = :db_condition_placeholder_2) )**AND**( (taxonomy_index_value_1.tid = :db_condition_placeholder_3) )))
ORDER BY node_created DESC

SELECT node.title AS node_title, node.nid AS nid, node.created AS node_created
FROM node node
OUTER JOIN taxonomy_index taxonomy_index_value_0 ON node.nid = taxonomy_index_value_0.nid AND taxonomy_index_value_0.tid = '9'
OUTER JOIN taxonomy_index taxonomy_index_value_1 ON node.nid = taxonomy_index_value_1.nid AND taxonomy_index_value_1.tid = '6'
WHERE ((( (taxonomy_index_value_0.tid = '9') )OR( (taxonomy_index_value_1.tid = '6') )))
ORDER BY node_created DESC LIMIT 5 OFFSET 0;

SELECT node.title AS node_title, node.nid AS nid, node.created AS node_created
FROM node node
LEFT OUTER JOIN taxonomy_index taxonomy_index_value_0 ON node.nid = taxonomy_index_value_0.nid AND taxonomy_index_value_0.tid = '9'
LEFT OUTER JOIN taxonomy_index taxonomy_index_value_1 ON node.nid = taxonomy_index_value_1.nid AND taxonomy_index_value_1.tid = '6'
WHERE ((( (taxonomy_index_value_0.tid = '9') )OR( (taxonomy_index_value_1.tid = '6') )))
ORDER BY node_created DESC LIMIT 5 OFFSET 0;

function custom_views_query_alter(&$view, &$query) {
    if($view->name == "tag_cloud"){
        print_r($query);// before modifying the query.
        $query->table_queue['taxonomy_index']['join']->type = "LEFT OUTER JOIN";
        //sample field change where  ever you want
        print_r($query);// after modifying the query .
    }
}