/**
 * In Drupal 6, `taxonomy_select_nodes` was able to filter by multiple terms,
 * but Drupal 7 accepts only one Term ID.
 */

function taxonomy_select_nodes_multiple($tids = array(), $operator = 'or'){
	$nids = array();
	if (variable_get('taxonomy_maintain_index_table', TRUE)){
		switch($operator){
			case 'or':
				$query = 'SELECT DISTINCT(nid) FROM {taxonomy_index} WHERE tid IN(' . implode(',', $tids) . ')';
			break;
			case 'and':
				$i = 0;
				foreach ($tids as $tid){
					if ($i == 0){
						$tables = 't0.nid FROM {taxonomy_index} t0 ';
						$where = "t0.tid = $tid ";
					} else {
						$tables .= "LEFT JOIN {taxonomy_index} t$i ON (t$i.nid = t".($i - 1).'.nid) ';
						$where .= "AND t$i.tid = $tid ";
					}
					$i ++;
				}
				$query = "SELECT $tables WHERE $where ORDER BY t0.nid ASC";
			break;
		}
	}	
	if (!empty($query)) $nids = db_query($query)->fetchCol();
	return $nids;
}

function taxonomy_select_nodes_multiple($tids = array(), $operator = 'or'){
	$nids = array();
	if (variable_get('taxonomy_maintain_index_table', TRUE)){
		switch($operator){
			case 'or':
				$query = 'SELECT DISTINCT(nid) FROM {taxonomy_index} WHERE tid IN(' . implode(',', $tids) . ')';
			break;
			case 'and':
				$i = 0;
				foreach ($tids as $tid){
					if ($i == 0){
						$tables = 't0.nid FROM {taxonomy_index} t0 ';
						$where = "t0.tid = $tid ";
					} else {
						$tables .= "LEFT JOIN {taxonomy_index} t$i ON (t$i.nid = t".($i - 1).'.nid) ';
						$where .= "AND t$i.tid = $tid ";
					}
					$i ++;
				}
				$query = "SELECT $tables WHERE $where ORDER BY t0.nid ASC";
			break;
		}
	}	
	if (!empty($query)) $nids = db_query($query)->fetchCol();
	return $nids;
}

function taxonomy_select_nodes_multiple($tids = array(), $operator = 'or'){
	$nids = array();
	if (variable_get('taxonomy_maintain_index_table', TRUE)){
		switch($operator){
			case 'or':
				$query = 'SELECT DISTINCT(nid) FROM taxonomy_index WHERE tid IN(' . implode(',', $tids) . ')';
			break;
			case 'and':
				$i = 0;
				foreach ($tids as $tid){
					if ($i == 0){
						$tables = 't0.nid FROM {taxonomy_index} t0 ';
						$where = "t0.tid = $tid ";
					} else {
						$tables .= "LEFT JOIN {taxonomy_index} t$i ON (t$i.nid = t".($i - 1).'.nid) ';
						$where .= "AND t$i.tid = $tid ";
					}
					$i ++;
				}
				$query = "SELECT $tables WHERE $where ORDER BY t0.nid ASC";
			break;
		}
	}	
	if (!empty($query)) $nids = db_query($query)->fetchCol();
	return $nids;
}

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**Important: this snipplet has moved to Github.**

 - [taxonomy_select_nodes with multiple terms, in Drupal 7](https://gist.github.com/1973248)

Drupal 7: taxonomy_select_nodes with multiple terms

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