学说：GROUP_CONCAT的CASE语法是什么？

Question

我有这样的SQL查询其在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 

而且我想这样做在教义和Symfony3，我试过，但我有情况下，当附近有语法错误。

$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(); 

或者这样：

'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' 

我还试图用IfElse和IFNULL扩展从beberlei/DoctrineExtensions bundle，但我无法找到正确的语法。

此查询在CASE WHEN时无效。

感谢您的帮助。

Answer 1

我觉得你的问题是用双引号在"NULL"，使用单引号和逃避他们：

$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();