MYSQL Grouping Merge function

from:http://blog.csdn.net/wwwyuanliang10000/article/details/27536175

Group_concat function in MySQL
The complete syntax is as follows:
Group_concat ([DISTINCT] field to connect [order by Asc/desc sort field] [Separator ' delimiter '])

Basic Query
Mysql> select * from AA;
+------+------+
| id| name |
+------+------+
| 10|
| 20|
| 20|
| 20|
|3 | 200 |
|3 | 500 |
+------+------+
6 rows in Set (0.00 sec)

Group by ID, print the value of the Name field on one line, comma separated (default)
Mysql> Select Id,group_concat (name) from the AA group by ID;
+------+--------------------+
| id| Group_concat (name) |
+------+--------------------+
| 10,20,20|
| 20 |
|3 | 200,500|
+------+--------------------+
3 Rows in Set (0.00 sec)

Group by ID, print the value of the Name field on one line, semicolon delimited
Mysql> Select ID,GROUP_CONCAT (name separator '; ') from the AA group by ID;
+------+----------------------------------+
| id| Group_concat (name separator '; ') |
+------+----------------------------------+
| 10;20;20 |
| 20|
|3 | 200;500 |
+------+----------------------------------+
3 Rows in Set (0.00 sec)

Group by ID, print the value of the redundant Name field to a line,
Comma delimited

Mysql> Select Id,group_concat (distinct name) from the AA group by ID;
+------+-----------------------------+
| id| Group_concat (distinct name) |
+------+-----------------------------+
| 10,20|
| 20 |
|3 | 200,500 |
+------+-----------------------------+
3 Rows in Set (0.00 sec)

Group by ID, print the value of the Name field in one line, comma separated, and reverse by name
Mysql> Select Id,group_concat (name order BY name Desc) from the AA group by ID;
+------+---------------------------------------+
| id| Group_concat (name order BY name Desc) |
+------+---------------------------------------+
| 20,20,10 |
| 20|
|3 | 500,200|
+------+---------------------------------------+
3 Rows in Set (0.00 sec)

MYSQL Grouping Merge function