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法律研究獲取唯一值的計數的 MySQL 查詢？
要計算列中的唯一值，需要使用關鍵字 DISTINCT。為了理解它是如何實現的，讓我們建立一個表。建立表的查詢如下 -
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記錄。查詢如下 -
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 語句顯示錶中的所有記錄。查詢如下 -
mysql> select *from UniqueCountByIPAddress;
以下是輸出 -
+----+----------+--------------+ | 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 | +----+----------+--------------+
以下是計算列 'UserIPAddress' 上唯一值數量的查詢 -
mysql> select UserHits,count(distinct UserIPAddress) as TotalHits -> from UniqueCountByIPAddress group by UserHits;
以下是輸出 -
+----------+-----------+ | UserHits | TotalHits | +----------+-----------+ | 10 | 1 | | 20 | 2 | | 30 | 1 | +----------+-----------+ 3 rows in set (0.05 sec)
更新日期: 30-Jul-2019
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