Using Hook Views Query Alter

Building a website I recently ran into an issue where I had HTML search facets interacting with Drupal views. The user would click on the facet and it would filter the view depending on the argument. I ended up implementing hook_views_query_alter. To make sure the values I wanted to filter on were in the view, I added the search facets into the view as fields. This automatically joins the necessary tables so that you don’t have to. Implementing hook_views_query_alter requires two parameters, view and query, both are passed by reference. Since this hook is called for every view the first thing I did was check that I was altering the right query by adding an if statement that checks the view name. After that you're free to modify the query as you wish. In my example, I looped through the search facets and added them as where statements and arguments to the query.

function search_views_query_alter(&$view, &$query) {
  if($view->name == 'example_view_name'){
    foreach($parsed_url AS $key => $value){ 
      where[0]['clauses'][] = 'profile_values_profile_' . $key . '.value IN ("%s")'; 
      where[0]['args'][] = $value; 
    }
  }
} 

One of the search facets was a taxonomy filter which the user was allowed to multi select. In order to get the view to grab the correct values, I had to add join clauses to dynamically create term_node table aliases. This is done by adding a join clause to the table_queue and tables array elements within the query object. I was able to just copy the existing term_node table_queue and tables array elements because I only wanted to create different aliases. Then I incremented the existing term_node table count within the tables array. If you wanted to create a new table join dynamically, the same approach is used but the table_queue and tables definitions need to be created by hand.

foreach($parsed_url AS $key => $value) { 
  $vid = _search_get_vocabulary_id(str_replace('_', ' ', $key)); 
  $tid = _search_get_term_by_vocabulary($vid, $value); 
  $table_term_node_join = $query->table_queue['term_node']; 
  $query->table_queue['term_node_' . $count] = $table_term_node_join; 
  $query->table_queue['term_node_' . $count]['alias'] = 'term_node_' . $count; $query->tables['term_node']['count']++; 
  $query->where[0]['args'][] = $tid->tid; 
  $query->where[0]['clauses'][] .= 'term_node_' . $count . '.tid = %d'; $count++; 
} 

 The query table_queue and tables array elements looks like so:

Table Queue:
'table_queue' => array (
   'term_node' => array (
     'table' => 'term_node',
     'num' => 1,
     'alias' => 'term_node',
     'join' => views_join::__set_state(array(
       'definition' => array (
       'left_field' => 'vid',
       'field' => 'vid',
       'table' => 'term_node',
       'left_table' => 'node',
     ),
     'extra_type' => 'AND',
     'table' => 'term_node',
     'left_table' => 'node',
     'left_field' => 'vid',
     'field' => 'vid',
     'type' => 'LEFT',
     'adjusted' => true,
     )
   )

Tables: 
'tables' => array (
     'node' => array (
       'node' => array (
       'count' => 1,
       'alias' => 'node',
       ),
     'term_node' => array (
       'count' => 1,
       'alias' => 'term_node',
     )
   ),
 ); 

In my book this makes views more comfortable to use because it gives me more control over them. This along with a view preprocessor allows me to style and output pretty much anything I want within a view.