1 mysql中的多行查詢結果合併成一個
 2 
 3 SELECT GROUP_CONCAT(md.data1) FROM DATA md,contacts cc WHERE md.conskey=cc.id AND md.mimetype_id= 5 AND md.user_id=17：
 4 
 5 利用函式：group_concat(),實現一個ID對應多個名稱時，原本為多行資料，把名稱合併成一行，如|1 | 10,20,20|
 6 
 7  
 8 
 9 本文通過例項介紹了MySQL中的group_concat函式的使用方法，比如select group_concat(name) 。
 
10 MySQL中group_concat函式
11 完整的語法如下：
12 group_concat([DISTINCT] 要連線的欄位 [Order BY ASC/DESC 排序欄位] [Separator '分隔符'])
13 
14 基本查詢 
15 mysql> select * from aa;
16 +------+------+
17 | id| name |
18 +------+------+
19 |1 | 10|
20 |1 | 20|
21 |1 | 20|
22 |2 | 20|
23 |3 | 200 |
24 |3 | 500 |
25 +------+------+
26 6
 
 rows in set (0.00 sec)
27 
28 以id分組，把name欄位的值列印在一行，逗號分隔(預設) 
29 mysql> select id,group_concat(name) from aa group by id;
30 +------+--------------------+
31 | id| group_concat(name) |
32 +------+--------------------+
33 |1 | 10,20,20|
34 |2 | 20 |
35 |3 | 200,500|
36 +------+--------------------+
37 3 rows in
 
 set (0.00 sec)
38 
39 以id分組，把name欄位的值列印在一行，分號分隔 
40 mysql> select id,group_concat(name separator ';') from aa group by id;
41 +------+----------------------------------+
42 | id| group_concat(name separator ';') |
43 +------+----------------------------------+
44 |1 | 10;20;20 |
45 |2 | 20|
46 |3 | 200;500 |
47 +------+----------------------------------+
48 3 rows in set (0.00 sec)
49 
50 以id分組，把去冗餘的name欄位的值列印在一行， 
51 逗號分隔
52 
53 mysql> select id,group_concat(distinct name) from aa group by id;
54 +------+-----------------------------+
55 | id| group_concat(distinct name) |
56 +------+-----------------------------+
57 |1 | 10,20|
58 |2 | 20 |
59 |3 | 200,500 |
60 +------+-----------------------------+
61 3 rows in set (0.00 sec)
62 
63 以id分組，把name欄位的值列印在一行，逗號分隔，以name排倒序 
64 mysql> select id,group_concat(name order by name desc) from aa group by id;
65 +------+---------------------------------------+
66 | id| group_concat(name order by name desc) |
67 +------+---------------------------------------+
68 |1 | 20,20,10 |
69 |2 | 20|
70 |3 | 500,200|
71 +------+---------------------------------------+
72 3 rows in set (0.00 sec)