mysql:查询来自2个表的组合信息
假设以下配置:mysql:查询来自2个表的组合信息,mysql,Mysql,假设以下配置: 表1“通用”字段:id和名称 表2带有字段的“信息”:userId(和其他一些) 当有信息要存储时,将有记录添加到信息表中。我可以很容易地获得每个用户记录数量的良好概述,如: mysql> SELECT userId ,COUNT(*) as nbr_entries FROM info GROUP BY userId ORDER BY nbr_entries DESC; +-----------+-------------+ | userId | nbr_entrie
mysql> SELECT userId ,COUNT(*) as nbr_entries FROM info GROUP BY userId ORDER BY nbr_entries DESC;
+-----------+-------------+
| userId | nbr_entries |
+-----------+-------------+
| 3987 | 2254 |
| 11220 | 1922 |
...
现在,我的问题是:我希望在表1(通用)中查找每个用户ID,以便我的查询结果如下:
+-----------+-----------+-------------+
| name | userId | nbr_entries |
+-----------+-----------+-------------+
| Peter | 3987 | 2254 |
| Walter | 11220 | 1922 |
...
你知道如何做到这一点吗?
提前感谢。您可以使用
加入
SELECT b.name,userid,COUNT(*) as nbr_entries FROM info a
inner join generic b on a.userid=b.id
GROUP BY b.name,userId
ORDER BY nbr_entries DESC;
SELECT t1.name, t2.userId , t2.nbr_entries
FROM generic t1
JOIN
(SELECT userId ,COUNT(*) as nbr_entries FROM info GROUP BY userId) t2
ON t1.userId = t2.userId ORDER BY t2.nbr_entries DESC;
您可以使用子查询
和加入
SELECT b.name,userid,COUNT(*) as nbr_entries FROM info a
inner join generic b on a.userid=b.id
GROUP BY b.name,userId
ORDER BY nbr_entries DESC;
SELECT t1.name, t2.userId , t2.nbr_entries
FROM generic t1
JOIN
(SELECT userId ,COUNT(*) as nbr_entries FROM info GROUP BY userId) t2
ON t1.userId = t2.userId ORDER BY t2.nbr_entries DESC;
使用左连接:
SELECT g.name, g.id as userId, COUNT(i.userId) as nbr_entries
FROM generic g
LEFT JOIN info i ON i.userId = g.id
GROUP BY g.id
ORDER BY nbr_entries DESC
这样,您还将包括没有信息条目(尚未)的用户,并以nbr\u条目的形式获取0