微客导航 » 文章资讯 » 获取MySQL列中唯一行的计数？

获取MySQL列中唯一行的计数？

2024-05-16 04:58:05 330

在MySQL中，COUNT()将显示行数。DISTINCT用于忽略重复的行并仅获取唯一行的计数。

让我们首先创建一个表：

mysql> create table DemoTable
(
   Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   FirstName varchar(10)
);

以下是使用insert命令在表中插入一些记录的查询：

mysql> insert into DemoTable(FirstName) values('Larry');
mysql> insert into DemoTable(FirstName) values('John');
mysql> insert into DemoTable(FirstName) values('Sam');
mysql> insert into DemoTable(FirstName) values('John');
mysql> insert into DemoTable(FirstName) values('John');
mysql> insert into DemoTable(FirstName) values('Larry');
mysql> insert into DemoTable(FirstName) values('Mike');
mysql> insert into DemoTable(FirstName) values('Robert');
mysql> insert into DemoTable(FirstName) values('Carol');

mysql> insert into DemoTable(FirstName) values('Mike');

以下是使用select命令显示表中记录的查询：

mysql> select *from DemoTable;

这将产生以下输出：

+----+-----------+
| Id | FirstName |
+----+-----------+
|  1 | Larry     |
|  2 | John      |
|  3 | Sam       |
|  4 | John      |
|  5 | John      |
|  6 | Larry     |
|  7 | Mike      |
|  8 | Robert    |
|  9 | Carol     |
| 10 | Mike      |
+----+-----------+
10 rows in set (0.00 sec)

以下是忽略COUNT个重复行并仅获取唯一行数的查询：

mysql> select count(distinct FirstName) from DemoTable;

这将产生以下输出：

+---------------------------+
| count(distinct FirstName) |
+---------------------------+
|                         6 |
+---------------------------+
1 row in set (0.03 sec)

返回顶部
3162201930
czq8825@qq.com

获取MySQL列中唯一行的计数？

热门推荐

随机推荐