MySQL计算一行中的2列并与另一个查询联接
我有一个表MySQL计算一行中的2列并与另一个查询联接,mysql,sql,join,count,union,Mysql,Sql,Join,Count,Union,我有一个表访问如下： +--------------+-------------+------+-----+---------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------------------+--------
访问+--------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| vis_id | int(11) | NO | | NULL | |
| unit | int(11) | NO | | NULL | |
| time_in | timestamp | NO | | CURRENT_TIMESTAMP | |
| time_out | timestamp | NO | | 0000-00-00 00:00:00 | |
| in_username | varchar(16) | NO | | NULL | |
| out_username | varchar(16) | NO | | NULL | |
+--------------+-------------+------+-----+---------------------+----------------+
+------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| fname | varchar(32) | NO | | NULL | |
| lname | varchar(32) | NO | | NULL | |
| date_added | timestamp | NO | | CURRENT_TIMESTAMP | |
| username | varchar(16) | NO | | NULL | |
| password | varchar(40) | NO | | NULL | |
| auth_level | int(1) | NO | | 1 | |
| last_login | timestamp | NO | | 0000-00-00 00:00:00 | |
+------------+-------------+------+-----+---------------------+----------------+
select count(*) as "count", u.fname as "fname"
from visits v
inner join users as u on u.username = v.in_username
group by u.username order by u.fname
+----------+-----------+----------+
| count_in | count_out | fname |
+----------+-----------+----------+
| 118 | 224 | Bo |
| 27 | 64 | James |
| 147 | 138 | Jeremy |
| 23 | 37 | Jim |
| 182 | 172 | Robert |
| 120 | 158 | Tom |
+----------+-----------+----------+
用户+--------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| vis_id | int(11) | NO | | NULL | |
| unit | int(11) | NO | | NULL | |
| time_in | timestamp | NO | | CURRENT_TIMESTAMP | |
| time_out | timestamp | NO | | 0000-00-00 00:00:00 | |
| in_username | varchar(16) | NO | | NULL | |
| out_username | varchar(16) | NO | | NULL | |
+--------------+-------------+------+-----+---------------------+----------------+
+------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| fname | varchar(32) | NO | | NULL | |
| lname | varchar(32) | NO | | NULL | |
| date_added | timestamp | NO | | CURRENT_TIMESTAMP | |
| username | varchar(16) | NO | | NULL | |
| password | varchar(40) | NO | | NULL | |
| auth_level | int(1) | NO | | 1 | |
| last_login | timestamp | NO | | 0000-00-00 00:00:00 | |
+------------+-------------+------+-----+---------------------+----------------+
select count(*) as "count", u.fname as "fname"
from visits v
inner join users as u on u.username = v.in_username
group by u.username order by u.fname
+----------+-----------+----------+
| count_in | count_out | fname |
+----------+-----------+----------+
| 118 | 224 | Bo |
| 27 | 64 | James |
| 147 | 138 | Jeremy |
| 23 | 37 | Jim |
| 182 | 172 | Robert |
| 120 | 158 | Tom |
+----------+-----------+----------+
in\u usernameout\u username+--------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| vis_id | int(11) | NO | | NULL | |
| unit | int(11) | NO | | NULL | |
| time_in | timestamp | NO | | CURRENT_TIMESTAMP | |
| time_out | timestamp | NO | | 0000-00-00 00:00:00 | |
| in_username | varchar(16) | NO | | NULL | |
| out_username | varchar(16) | NO | | NULL | |
+--------------+-------------+------+-----+---------------------+----------------+
+------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| fname | varchar(32) | NO | | NULL | |
| lname | varchar(32) | NO | | NULL | |
| date_added | timestamp | NO | | CURRENT_TIMESTAMP | |
| username | varchar(16) | NO | | NULL | |
| password | varchar(40) | NO | | NULL | |
| auth_level | int(1) | NO | | 1 | |
| last_login | timestamp | NO | | 0000-00-00 00:00:00 | |
+------------+-------------+------+-----+---------------------+----------------+
select count(*) as "count", u.fname as "fname"
from visits v
inner join users as u on u.username = v.in_username
group by u.username order by u.fname
+----------+-----------+----------+
| count_in | count_out | fname |
+----------+-----------+----------+
| 118 | 224 | Bo |
| 27 | 64 | James |
| 147 | 138 | Jeremy |
| 23 | 37 | Jim |
| 182 | 172 | Robert |
| 120 | 158 | Tom |
+----------+-----------+----------+
。。。如果可能的话，我希望在同一个查询中同时使用这两种方法，以便得到如下结果：
+--------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| vis_id | int(11) | NO | | NULL | |
| unit | int(11) | NO | | NULL | |
| time_in | timestamp | NO | | CURRENT_TIMESTAMP | |
| time_out | timestamp | NO | | 0000-00-00 00:00:00 | |
| in_username | varchar(16) | NO | | NULL | |
| out_username | varchar(16) | NO | | NULL | |
+--------------+-------------+------+-----+---------------------+----------------+
+------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| fname | varchar(32) | NO | | NULL | |
| lname | varchar(32) | NO | | NULL | |
| date_added | timestamp | NO | | CURRENT_TIMESTAMP | |
| username | varchar(16) | NO | | NULL | |
| password | varchar(40) | NO | | NULL | |
| auth_level | int(1) | NO | | 1 | |
| last_login | timestamp | NO | | 0000-00-00 00:00:00 | |
+------------+-------------+------+-----+---------------------+----------------+
select count(*) as "count", u.fname as "fname"
from visits v
inner join users as u on u.username = v.in_username
group by u.username order by u.fname
+----------+-----------+----------+
| count_in | count_out | fname |
+----------+-----------+----------+
| 118 | 224 | Bo |
| 27 | 64 | James |
| 147 | 138 | Jeremy |
| 23 | 37 | Jim |
| 182 | 172 | Robert |
| 120 | 158 | Tom |
+----------+-----------+----------+
其中count\u in
是他们的用户名在访问中出现的次数。in\u username
和count\u out
是他们的用户名在访问中出现的次数。out\u username
我用UNION
尝试的所有方法似乎都将计数相加，或者出于某种原因删除了行。有什么想法吗？进行子查询以获得每个总数，将它们与UNION
组合，然后将它们与SUM（）
合并
太好了，这正是我需要的。。。我以前没有看到过combined
，这是MySQL关键字吗？子查询需要有别名，仅此而已。