MySQL 如何使用单个查询将行折叠成逗号分隔列表

使用GROUP_CONCAT()将行折叠为逗号分隔列表。让我们先创建一个表 –

mysql> create table DemoTable
(
   Id int,
   Name varchar(40)
);
Query OK, 0 rows affected (0.52 sec)

使用insert命令在表中插入一些记录 –

mysql> insert into DemoTable values(100,'Chris Brown');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable values(101,'Adam Smith');
Query OK, 1 row affected (0.84 sec)
mysql> insert into DemoTable values(101,'John Doe');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values(100,'David Miller');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable values(101,'Carol Taylor');
Query OK, 1 row affected (0.22 sec)
mysql> insert into DemoTable values(103,'Bob Taylor');
Query OK, 1 row affected (0.20 sec)

使用select语句显示表中的所有记录 –

mysql> select *from DemoTable;

这将产生以下输出 –

+------+--------------+
| Id   | Name         |
+------+--------------+
|  100 | Chris Brown |
|  101 | Adam Smith  |
|  101 | John Doe    |
|  100 | David Miller|
|  101 | Carol Taylor|
|  103 | Bob Taylor  |
+------+--------------+
6 rows in set (0.00 sec)

以下是折叠行为逗号分隔列表的查询 –

mysql> select Id,group_concat(Name) from DemoTable group by Id;

这将会产生以下输出 –

+------+----------------------------------+
| Id   | group_concat(Name)               |
+------+----------------------------------+
|  100 | Chris Brown,David Miller         |
|  101 | Adam Smith,John Doe,Carol Taylor |
|  103 | Bob Taylor                       |
+------+----------------------------------+
3 rows in set (0.00 sec)