Adds the base entity table to a field query object.
SelectQuery $select_query: A SelectQuery containing at least one table as specified by _field_sql_storage_tablename().
$entity_type: The entity type for which the base table should be joined.
$field_base_table: Name of a table in $select_query. As only INNER JOINs are used, it does not matter which.
The name of the entity base table joined in.
function _field_sql_storage_query_join_entity(SelectQuery $select_query, $entity_type, $field_base_table) {
$entity_info = entity_get_info($entity_type);
$entity_base_table = $entity_info['base table'];
$entity_field = $entity_info['entity keys']['id'];
$select_query
->join($entity_base_table, $entity_base_table, "{$entity_base_table}.{$entity_field} = {$field_base_table}.entity_id");
return $entity_base_table;
}