Question

我在MySQL中有表格，我希望获得有关查找3个用户的使用限制的统计数据

过去一小时内用于登录的不同IP地址（列ip）
过去一天用户的帖子数量（列cnt）
过去10分钟内用户的会话数（列authid是用户名）

由于输入控制对象的原因我需要这三行，所以我开始使用MySQL UNION但是我得到了奇怪的结果。这就是我所拥有的

mysql> desc senderlimits;
+----------+--------------+------+-----+-------------------+-------+
| Field    | Type         | Null | Key | Default           | Extra |
+----------+--------------+------+-----+-------------------+-------+
| authid   | varchar(128) | NO   |     | NULL              |       |
| ip       | varchar(40)  | NO   |     | NULL              |       |
| cnt      | int(11)      | NO   |     | 1                 |       |
| datetime | timestamp    | NO   |     | CURRENT_TIMESTAMP |       |
+----------+--------------+------+-----+-------------------+-------+
4 rows in set (0.00 sec)

mysql> select count(distinct ip) as ipl from senderlimits where authid='bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 1 hour) UNION select sum(cnt) as cntl from senderlimits where authid='bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 24 hour) UNION select sum(cnt) as vcnt from senderlimits where authid='bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 10 minute) ;
+------+
| ipl  |
+------+
|    1 |
|   95 |
+------+
2 rows in set (0.04 sec)

mysql> select count(distinct ip) as ipl from senderlimits where authid='cincinnati@psmail.net' and datetime > date_sub(now(),INTERVAL 1 hour);
+-----+
| ipl |
+-----+
|   0 |
+-----+
1 row in set (0.01 sec)

mysql> select sum(cnt) as cntl from senderlimits where authid='bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 24 hour) ;
+------+
| cntl |
+------+
|   95 |
+------+
1 row in set (0.02 sec)

mysql> select count(authid) as vcnt from senderlimits where authid='bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 10 minute);
+------+
| vcnt |
+------+
|    1 |
+------+
1 row in set (0.02 sec)

mysql>

使用UNION选项时，结果非常奇怪。有专家知道为什么吗？或者我如何能够获得相同的结果 0 95 1

按此顺序？

Answer 1

UNION删除重复项。你想要UNION ALL：

select count(distinct ip) as ipl
from senderlimits
where authid = 'bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 1 hour)
UNION ALL
select sum(cnt) as cntl
from senderlimits
where authid = 'bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 24 hour)
UNION ALL
select sum(cnt) as vcnt
from senderlimits
where authid = 'bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 10 minute) ;

但是，您不应该依赖于结果的顺序与子查询的顺序相同（这不保证，即使它经常在实践中发生）。您应该包含一个列，指定哪个数字代表什么：

select '1 hour' as which, count(distinct ip) as ipl
from senderlimits
where authid = 'bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 1 hour)
UNION ALL
select '24 hour' as which, sum(cnt) as cntl
from senderlimits
where authid = 'bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 24 hour)
UNION ALL
select '10 minutes' as which, sum(cnt) as vcnt
from senderlimits
where authid = 'bob@nsd.clear.net' and datetime > date_sub(now(),INTERVAL 10 minute) ;

MySQL SQL Union给出了奇怪的结果

1 个答案: