protected function buildColumns() {
		$select = [];
		$params = [];
		if(!$this->columns)
			return ['*', []];
		else {
			foreach($this->columns as $alias=>$column) {
				if($column instanceof static) {
					$sql = $column->buildSQL();
					$params = array_merge($params, $column->getParameters());
					$select[] = '('.$sql.') AS '.$this->identifierQuotes($alias);
				}
				elseif($column instanceof Raw) {
					$sql = $column->getSQL();
					$params = array_merge($params, $column->getParameters());
					$select[] = $sql.' AS '.$this->identifierQuotes($alias);
				}
				elseif((string)$alias !== (string)$column)
					$select[] = $this->identifierQuotes($column).' AS '.$this->identifierQuotes($alias);
				else
					$select[] = $this->identifierQuotes($column);
			}
		}
		return [implode(', ', $select), $params];
	}
protected function buildColumns() {
		$select = [];
		$params = [];
		if(!$this->columns)
			return ['*', []];
		else {
			foreach($this->columns as $alias=>$column) {
				if($column instanceof static) {
					$sql = $column->buildSQL();
					$params = array_merge($params, $column->getParameters());
					$select[] = '('.$sql.') AS '.$this->identifierQuotes($alias);
				}
				elseif($column instanceof Raw) {
					$sql = $column->getSQL();
					$params = array_merge($params, $column->getParameters());
					$select[] = $sql.' AS '.$this->identifierQuotes($alias);
				}
				elseif((string)$alias !== (string)$column)
					$select[] = $this->identifierQuotes($column).' AS '.$this->identifierQuotes($alias);
				else
					$select[] = $this->identifierQuotes($column);
			}
		}
		return [implode(', ', $select), $params];
	}
protected function buildColumns ( ) { $ select = [ ] ; $ params = [ ] ; if ( ! $ this -> columns ) return [ '*' , [ ] ] ; else { foreach ( $ this -> columns as $ alias => $ column ) { if ( $ column instanceof static ) { $ sql = $ column -> buildSQL ( ) ; $ params = array_merge ( $ params , $ column -> getParameters ( ) ) ; $ select [ ] = '(' . $ sql . ') AS ' . $ this -> identifierQuotes ( $ alias ) ; } elseif ( $ column instanceof Raw ) { $ sql = $ column -> getSQL ( ) ; $ params = array_merge ( $ params , $ column -> getParameters ( ) ) ; $ select [ ] = $ sql . ' AS ' . $ this -> identifierQuotes ( $ alias ) ; } elseif ( ( string ) $ alias !== ( string ) $ column ) $ select [ ] = $ this -> identifierQuotes ( $ column ) . ' AS ' . $ this -> identifierQuotes ( $ alias ) ; else $ select [ ] = $ this -> identifierQuotes ( $ column ) ; } } return [ implode ( ', ' , $ select ) , $ params ] ; }
Build the list of columns.
@return string
Build the list of columns .