MySQL 利用group_concat函数进行合并行 （转）
转载： http://hchmsguo.iyunv.com/blog/555543MySQL中group_concat函数，能将相同的行组合起来。
完整的语法如下：
group_concat( 要连接的字段 )
基本查询
Sql代码
[*]select * from aa;
+------+------+
| id| name |
+------+------+
|1 | 10|
|1 | 20|
|1 | 20|
|2 | 20|
|3 | 200 |
|3 | 500 |
+------+------+
6 rows in set (0.00 sec)
以id分组，把name字段的值打印在一行，逗号分隔(默认)
Sql代码
[*]select id,group_concat(name) from aa group by id;
+------+--------------------+
| id| group_concat(name) |
+------+--------------------+
|1 | 10,20,20|
|2 | 20 |
|3 | 200,500|
+------+--------------------+
3 rows in set (0.00 sec)
以id分组，把name字段的值打印在一行，分号分隔
Java代码
[*]select id,group_concat(name separator ';') from aa group by id;
+------+----------------------------------+
| id| group_concat(name separator ';') |
+------+----------------------------------+
|1 | 10;20;20 |
|2 | 20|
|3 | 200;500 |
+------+----------------------------------+
3 rows in set (0.00 sec)
以id分组，把去冗余的name字段的值打印在一行，
逗号分隔
Sql代码
[*]select id,group_concat(distinct name) from aa group by id;
+------+-----------------------------+
| id| group_concat(distinct name) |
+------+-----------------------------+
|1 | 10,20|
|2 | 20 |
|3 | 200,500 |
+------+-----------------------------+
3 rows in set (0.00 sec)
以id分组，把name字段的值打印在一行，逗号分隔，以name排倒序
Sql代码
[*]select id,group_concat(name order by name desc) from aa group by id;
+------+---------------------------------------+
| id| group_concat(name order by name desc) |
+------+---------------------------------------+
|1 | 20,20,10 |
|2 | 20|
|3 | 500,200|
+------+---------------------------------------+
3 rows in set (0.00 sec)
测试sql，项目中用到的。
Sql代码
[*]SELECT
[*] EMPLOYEES.EMPID
[*] ,EMPLOYEES.EMPNAME
[*] ,DEPARTMENTS.DEPARTMENTNAME
[*] ,EMPLOYEES.DEPTID
[*] ,EMPLOYEES.EMPPWD
[*] ,EMPLOYEES.INSIDEEMAIL
[*] ,EMPLOYEES.OUTSIDEEMAIL
[*] ,EMPLOYEES.DELEFLAG
[*] ,EMPLOYEES.EMPCLASS
[*] ,(CONCAT('[', <span style="color: #ff0000;">GROUP_CONCAT</span>
[*](ROLE.Role_Name SEPARATOR '],['), ']')) AS ROLENAME
[*] ,(concat( '[', (
[*] SELECT
[*] <span style="color: #ff0000;">GROUP_CONCAT</span>
[*](DEPARTMENTS.DEPARTMENTNAME separator '],[')
[*] FROM
[*] EMP_ROLE_DEPT
[*] LEFT JOIN DEPARTMENTS
[*] ON (
[*] DEPARTMENTS.DEPARTMENTID = EMP_ROLE_DEPT.DEPTID
[*] AND DEPARTMENTS.DELEFLAG = 0
[*] )
[*] GROUP BY
[*] EMP_ROLE_DEPT.EMPID
[*] HAVING
[*] EMP_ROLE_DEPT.EMPID = EMPLOYEES.EMPID
[*] ),']')) AS DEPARTMENTRIGHT
[*] FROM
[*] EMPLOYEES
[*] LEFT JOIN DEPARTMENTS
[*] ON (
[*] DEPARTMENTS.DEPARTMENTID = EMPLOYEES.DEPTID
[*] AND DEPARTMENTS.DELEFLAG = 0
[*] )
[*] LEFT JOIN ROLE_EMP
[*] ON (ROLE_EMP.EMP_ID = EMPLOYEES.EMPID)
[*] LEFT JOIN ROLE
[*] ON (ROLE_EMP.ROLE_ID = ROLE.ROLE_ID)
[*]<span style="color: #ff0000;"> GROUP BY
[*] EMPLOYEES.EMPID</span>
[*]
[*] HAVING
[*] EMPLOYEES.EMPID LIKE '%%'
[*] AND EMPLOYEES.EMPNAME LIKE '%%'
[*] AND EMPLOYEES.DELEFLAG = 0
[*] AND (
[*] EMPLOYEES.EMPCLASS = '1'
[*] OR EMPLOYEES.EMPCLASS = '2'
[*] )
[*] AND EMPLOYEES.DEPTID = '001' LIMIT 0
[*] ,16
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