src/Data/BizDataSql.php
public function addSqlExpression($sqlExpr, $alias=null)
    {
        if ($alias)
            $sqlExpr .= ' AS '.$alias;
        if (!$this->_tableColumns)
            $this->_tableColumns = $sqlExpr;
        else
            $this->_tableColumns .= ", ".$sqlExpr;
    }
public function addSqlExpression($sqlExpr, $alias=null)
    {
        if ($alias)
            $sqlExpr .= ' AS '.$alias;
        if (!$this->_tableColumns)
            $this->_tableColumns = $sqlExpr;
        else
            $this->_tableColumns .= ", ".$sqlExpr;
    }
Add SQL expression in the sql statement
sqlExpr has format of "...join1.column1, ... join2.column2...". Replace join with alias

@param string $sqlExpr sql expression
@param string $alias sql alias
@return void