MySQL 查询获取唯一值的数量?
mysqlmysqli database
要计算列上的唯一值，您需要使用关键字 DISTINCT。要了解如何执行此操作，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) -> ); Query OK, 0 rows affected (0.69 sec)
使用 insert 命令在表中插入一些记录。 查询语句如下 −
mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(10,'127.0.0.1'); Query OK, 1 row affected (0.20 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(10,'127.0.0.1'); Query OK, 1 row affected (0.20 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.1'); Query OK, 1 row affected (0.20 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.1'); Query OK, 1 row affected (0.17 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.2'); Query OK, 1 row affected (0.13 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(20,'127.0.0.2'); Query OK, 1 row affected (0.20 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(30,'127.0.0.2'); Query OK, 1 row affected (0.17 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(30,'127.0.0.2'); Query OK, 1 row affected (0.28 sec) mysql> insert into UniqueCountByIPAddress(UserHits,UserIPAddress) values(30,'127.0.0.2'); Query OK, 1 row affected (0.14 sec)
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 | +----+----------+--------------+
以下是计算‘UserIPAddress’列中不同值的查询。 −
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)
