MySQL查询获取唯一值的计数？
要计算列上的唯一值，您需要使用关键字DISTINCT。要了解它是如何完成的，让我们创建一个表。创建表的查询如下-
mysql> create table UniqueCountByIPAddress -> ( -> Id int NOT NULL AUTO_INCREMENT, -> UserHits int, -> UserIPAddress varchar(50), -> PRIMARY KEY(Id) -> );
使用insert命令在表中插入一些记录。查询如下-
mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(10,'127.0.0.1'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(10,'127.0.0.1'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.1'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.1'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.2'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.2'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(30,'127.0.0.2'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(30,'127.0.0.2'); mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(30,'127.0.0.2');
使用select语句显示表中的所有记录。查询如下-
mysql> select *from UniqueCountByIPAddress;
以下是输出-
+----+----------+--------------+ | Id | UserHits | UserIPAddress| +----+----------+--------------+ | 1 | 10 | 127.0.0.1 | | 2 | 10 | 127.0.0.1 | | 3 | 20 | 127.0.0.1 | | 4 | 20 | 127.0.0.1 | | 5 | 20 | 127.0.0.2 | | 6 | 20 | 127.0.0.2 | | 7 | 30 | 127.0.0.2 | | 8 | 30 | 127.0.0.2 | | 9 | 30 | 127.0.0.2 | +----+----------+--------------+
以下是查询以计算'UserIPAddress'列上的不同值-
mysql> select UserHits,count(distinct UserIPAddress) as TotalHits -> from UniqueCountByIPAddress group by UserHits;
以下是输出-
+----------+-----------+ | UserHits | TotalHits | +----------+-----------+ | 10 | 1 | | 20 | 2 | | 30 | 1 | +----------+-----------+ 3 rows in set (0.05 sec)
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