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MySQL查询来计数具有特定列的行？

2024-04-23 03:08:05 421

让我们首先创建一个表-

mysql> create table DemoTable841(
   Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   Value varchar(100)
);

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable841(Value) values('X');
mysql> insert into DemoTable841(Value) values('Y');
mysql> insert into DemoTable841(Value) values('Y');
mysql> insert into DemoTable841(Value) values('Z');
mysql> insert into DemoTable841(Value) values('X');
mysql> insert into DemoTable841(Value) values('Z');

使用select语句显示表中的所有记录-

mysql> select *from DemoTable841;

这将产生以下输出-

+----+-------+
| Id | Value |
+----+-------+
|  1 | X     |
|  2 | Y     |
|  3 | Y     |
|  4 | Z     |
|  5 | X     |
|  6 | Z     |
+----+-------+
6 rows in set (0.00 sec)

以下是对MySQL中具有特定列的行进行计数的查询-

mysql> select Value,Concat(COUNT(Value),' Times') from DemoTable841 group by Value;

这将产生以下输出-

+-------+-------------------------------+
| Value | Concat(COUNT(Value),' Times') |
+-------+-------------------------------+
| X     | 2 Times                       |
| Y     | 2 Times                       |
| Z     | 2 Times                       |
+-------+-------------------------------+
3 rows in set (0.04 sec)

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MySQL查询来计数具有特定列的行？

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