LazyRecord\BaseCollection::join PHP Method

    public function join($target, $type = 'LEFT', $alias = null, $relationId = null)
    {
        $this->explictSelect = true;
        $query = $this->getCurrentReadQuery();
        // for models and schemas join
        if (is_object($target)) {
            $table = $target->getTable();
            /* XXX: should get selected column names by default, if not get all column names */
            $columns = $target->getColumnNames();
            $joinAlias = $alias ?: $table;
            if (!empty($columns)) {
                $select = array();
                foreach ($columns as $name) {
                    // Select alias.column as alias_column
                    $select[$joinAlias . '.' . $name] = $joinAlias . '_' . $name;
                }
                $query->select($select);
            }
            $joinExpr = $query->join($table, $joinAlias, $type);
            // it returns JoinExpression object
            // here the relationship is defined, join the it.
            if ($relationId) {
                if ($relation = $this->getSchema()->getRelation($relationId)) {
                    $joinExpr->on()->equal($this->_alias . '.' . $relation['self_column'], array($joinAlias . '.' . $relation['foreign_column']));
                } else {
                    throw new Exception("Relationship '{$relationId}' not found.");
                }
            } else {
                // find the related relatinship from defined relatinpships
                $relations = $this->getSchema()->relations;
                foreach ($relations as $relationId => $relation) {
                    if (!isset($relation['foreign_schema'])) {
                        continue;
                    }
                    $fschema = new $relation['foreign_schema']();
                    if (is_a($target, $fschema->getModelClass())) {
                        $joinExpr->on()->equal($this->_alias . '.' . $relation['self_column'], array($alias . '.' . $relation['foreign_column']));
                        break;
                    }
                }
            }
            if ($joinAlias) {
                $joinExpr->as($joinAlias);
            }
            return $joinExpr;
        } else {
            // For table name join
            $joinExpr = $query->join($target, $type);
            if ($alias) {
                $joinExpr->as($alias);
            }
            return $joinExpr;
        }
    }