學說：GROUP_CONCAT的CASE語法是什麼？

Question

我有這樣的SQL查詢其在phpMyAdmin正常工作：

SELECT `Tag_Type_Code`, `Tag_Type`, 
    GROUP_CONCAT(`Tag_Code` ORDER BY `Tag_Name`) as tagCode, 
    GROUP_CONCAT(`Tag_Name` ORDER BY `Tag_Name`) as tagName, 
    GROUP_CONCAT(CASE WHEN isnull(`Tag_Picto`) THEN 'NULL' ELSE `Tag_Picto` END ORDER BY `Tag_Name`) as tagPicto 
FROM tags 
WHERE `modele_code` = "MYCODE" 
GROUP BY `Tag_Type_Code` 
ORDER BY `tag_Type` ASC 

而且我想這樣做在教義和Symfony3，我試過，但我有情況下，當附近有語法錯誤。

$this->getEntityManager()->createQuery(
    'SELECT tag.typeCode, tag.type, 
     GROUP_CONCAT(tag.code ORDER BY tag.name) as tagCode, 
     GROUP_CONCAT(tag.name ORDER BY tag.name) as tagName, 
     GROUP_CONCAT(CASE WHEN tag.picto IS NULL THEN "NULL" ELSE tag.picto END ORDER BY tag.name) as tagPicto 
    FROM AppBundle:Tag tag 
    WHERE tag.modelCode = :code 
    GROUP BY tag.typeCode 
    ORDER BY tag.type ASC' 
)->setParameter('code', $modelCode) 
->getResult(); 

或者這樣：

'SELECT tag.typeCode, tag.type, 
    CASE WHEN tag.picto IS NULL THEN "NULL" ELSE tag.picto END as picto 
    GROUP_CONCAT(tag.code ORDER BY tag.name) as tagCode, 
    GROUP_CONCAT(tag.name ORDER BY tag.name) as tagName, 
    GROUP_CONCAT(picto ORDER BY tag.name) as tagPicto 
FROM AppBundle:Tag tag 
WHERE tag.modelCode = :code 
GROUP BY tag.typeCode 
ORDER BY tag.type ASC' 

我還試圖用IfElse和IFNULL擴展從beberlei/DoctrineExtensions bundle，但我無法找到正確的語法。

此查詢在CASE WHEN時無效。

感謝您的幫助。

Answer 1

我覺得你的問題是用雙引號在"NULL"，使用單引號和逃避他們：

$this->getEntityManager()->createQuery(
    'SELECT tag.typeCode, tag.type, 
     GROUP_CONCAT(tag.code ORDER BY tag.name) as tagCode, 
     GROUP_CONCAT(tag.name ORDER BY tag.name) as tagName, 
     GROUP_CONCAT(CASE WHEN tag.picto IS NULL THEN \'NULL\' ELSE tag.picto END ORDER BY tag.name) as tagPicto 
    FROM AppBundle:Tag tag 
    WHERE tag.modelCode = :code 
    GROUP BY tag.typeCode 
    ORDER BY tag.type ASC' 
)->setParameter('code', $modelCode) 
->getResult();