LEFT JOIN 时的情况？

Question

我想 select 左连接 table 取决于来自其他 table 的值。 所以我尝试了这个，但没有用：

CASE WHEN c.catId LIKE "%s%" THEN 
  LEFT JOIN AppBundle:newspaper_subcategories cat WITH c.catIdShort = cat.id
ELSE 
  LEFT JOIN AppBundle:newspaper_categories cat WITH c.catIdShort = cat.id
END

Answer 1

简单地左连接两个表，但在列子句上使用 CASE 语句

SELECT 
  . . . 
 CASE WHEN c.catId LIKE '%s%' 
 THEN sub.somecolumn
 ELSE cat.somecolumn
 END
  . . . 
LEFT JOIN AppBundle:newspaper_subcategories sub ON c.catIdShort = cat.id
LEFT JOIN AppBundle:newspaper_categories cat ON c.catIdShort = cat.id