Zend Framework按情形分組

Question

我無法使用zend框架mysql groupby查詢。我試圖做到的，是這個查詢

SELECT * FROM `price_list` AS `pl` 
GROUP BY 
CASE WHEN `pl`.`sub_folder` IS NULL THEN 
`pl`.`id` 
ELSE 
`pl`.`sub_folder` 
END 
ORDER BY `pl`.`date_added` DESC 

以下是我在Zend的方式試圖

$sql = $this->select()->setIntegrityCheck(false);  
$sql->from(array('pl'=>$this->_name), array('')) 
    ->columns($cols) 
    ->group("case when pl.sub_folder is null then pl.id else pl.sub_folder end"); 

但輸出這個SQL字符串的情況下，狀態錯誤報價：

SELECT * FROM `price_list_pdf` AS `pl` 
GROUP BY `CASE WHEN pl`.`sub_folder is null then 
pl`.`id 
ELSE 
pl`.`sub_folder 
end` 
ORDER BY `pl`.`date_added` DESC 

如何在字符串中清除這個`？還是有什麼更好的辦法呢？請幫助..

Answer 1

對於轉義querys使用Expressions像

$sql = $this->select()->setIntegrityCheck(false);  
$sql->from(array('pl'=>$this->_name), array('')) 
     ->columns($cols) 
     ->group(new Zend_Db_Expr("case when pl.sub_folder is null then pl.id else pl.sub_folder end"));