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GROUP BY MySQL中GROUP BY返回的行数？

2024-05-02 02:15:04 361

您可以为此使用GROUP_CONCAT()。为了理解上述概念，让我们创建一个表。

创建表的查询如下

mysql> create table groupByDemo
   -> (
   -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   -> Name varchar(100)
   -> );

使用insert命令在表中插入一些记录。

查询如下

mysql> insert into groupByDemo(Name) values('John');
mysql> insert into groupByDemo(Name) values('Carol');
mysql> insert into groupByDemo(Name) values('Carol');
mysql> insert into groupByDemo(Name) values('Bob');
mysql> insert into groupByDemo(Name) values('Bob');
mysql> insert into groupByDemo(Name) values('Bob');
mysql> insert into groupByDemo(Name) values('John');
mysql> insert into groupByDemo(Name) values('John');
mysql> insert into groupByDemo(Name) values('John');
mysql> insert into groupByDemo(Name) values('Sam');
mysql> insert into groupByDemo(Name) values('Carol');

使用select语句显示表中的所有记录。

查询如下

mysql> select *from groupByDemo;

以下是输出

+----+-------+
| Id | Name  |
+----+-------+
| 1  | John  |
| 2  | Carol |
| 3  | Carol |
| 4  | Bob   |
| 5  | Bob   |
| 6  | Bob   |
| 7  | John  |
| 8  | John  |
| 9  | John  |
| 10 | Sam   |
| 11 | Carol |
+----+-------+
11 rows in set (0.00 sec)

这是按行数分组的查询

mysql> SELECT Counter, GROUP_CONCAT(Name SEPARATOR ', ') as AllName
   -> FROM (SELECT Name, COUNT(Name) as Counter
      -> FROM groupByDemo
      -> GROUP BY Name) tbl
   -> GROUP BY Counter
   -> ORDER BY Counter DESC;

以下是输出

+---------+------------+
| Counter | AllName    |
+---------+------------+
| 4       | John       | 
| 3       | Carol, Bob |
| 1       | Sam        |
+---------+------------+
3 rows in set (0.00 sec)

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GROUP BY MySQL中GROUP BY返回的行数？

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