在MySQL查询中按问题分组

Question

我在查询时遇到麻烦：

SELECT a.created_by, 
CASE WHEN a.created_by_alias > ' ' THEN a.created_by_alias ELSE ua.name END AS author 
FROM #__content AS a 
LEFT JOIN #__users AS ua ON ua.id = a.created_by 
WHERE a.state='1' 
GROUP BY a.created_by 
ORDER BY author

返回的结果在某种程度上是正确的，但问题是它按ID分组，但仍返回重复的某些名称（这些名称相同，但具有不同的ID）。

如果这些名称具有不同的ID，如何将它们分组？

在此先感谢您的帮助。

Answer 1

也按作者分组

SELECT 
    a.created_by, 
    CASE WHEN a.created_by_alias > ' ' THEN a.created_by_alias ELSE ua.name END AS author 
FROM #__content AS a 
LEFT JOIN #__users AS ua ON ua.id = a.created_by 
WHERE a.state='1' 
GROUP BY a.created_by ,author
ORDER BY author