将2个结果集的结果与通用属性mySQL合并

Question

我正在尝试将使用SQL查询获得的两个结果集组合到一个结果集中。集合各有2列。第一组包含昵称和帖子，而另一组是昵称和评论。如何将这两个集合结合起来显示每个昵称有多少帖子和评论？最终结果集应包含：昵称，帖子，评论。

第一组：

SELECT u.nickname, COUNT(c.nickname) AS comments 
 FROM postcomments c, users u WHERE c.nickname = u.nickname 
GROUP BY nickname;

第二组：

SELECT u.nickname, COUNT(*) AS posts 
 FROM postauthors a, users u WHERE a.nickname = u.nickname 
GROUP BY u.nickname;

Answer 1

您可以使用JOIN来完成

SELECT u.nickname, COUNT(c.id) AS comments,count(a.id) AS posts 
 FROM users u
 LEFT JOIN postcomments c ON c.nickname = u.nickname
 LEFT JOIN postauthors a ON a.nickname=u.nickname
GROUP BY u.nickname;